There are several aspects of cryptic diversity and speciation.

First, we have to keep in mind that cryptic diversity may refer to the diversity of phylogenetic lineages at various stages of speciation. Many species are metapopulations composed of more or less isolated populations. This isolation may be more or less strict and may last from hundreds to thousands or even millions of years. With time, such populations may even become highly differentiated or even divergent (at the molecular level) but still may retain the potential to interbreed when the isolation ends. Thus, indeed we may observe completely different genetic pools but only experiments will show whether such populations will really interbreed. On the other side, we know that even species that are clearly different with respect to their morphology and even habitat, may interbreed occasionally and incorporate part of the genetic pool from the other species. There is an interesting paper about the origin of European bison that deals with such an issue (DOI: 10.1038/ncomms13158).

Second, a large part of the cryptic species is obviously cryptic from our, subjective, visually-biased, perspective. The species may really differ in their physiology, pheromone system, behaviour etc., or even in some morphological details that we haven't perceived so far... Sometimes the morphological differences become obvious after we find out coherent differences at the molecular level... On the other side, there are cases of morphospecies that do not differ at the molecular level (of course it concerns only the markers that were used).

Third, in taxonomy, species is a testable hypothesis. We always need to remember, that we may be wrong defining a particular species, doesn't matter whether based on morphology, DNA or both...

Concluding I believe, that we are still far from understanding of the nature of speciation and of species... But that's the beauty of being a scientist ;-)

Jean-Francois,

You explained everything.

"Cryptic speciation is a biological process that results in a group of species (which, by definition, cannot interbreed) that contain individuals that are morphologically identical to each other but belong to different species"

A good example of cryptic speciation is that of the Two-barred Flasher butterfly (Astraptes fulgerator). Despite adult butterflies having an identical appearance DNA analysis has suggested that there are at least three different species of this butterfly"

Problems and Questions Posed by Cryptic Species. A Framework to Guide Future Studies

(https://link.springer.com/chapter/10.1007/978-3-030-10991-2_4)

Ten species in one: DNA barcoding reveals cryptic species in the neotropical skipper butterfly Astraptes fulgerator

(https://www.pnas.org/content/pnas/101/41/14812.full.pdf)

'Hidden' species may be surprisingly common

(https://www.newscientist.com/article/dn12293-hidden-species-may-be-surprisingly-common/)

Yes, they probably exist, but certainly not even approximately as frequently as claimed by molecular biologists who seem to routinely misinterpret DNA-sequences (geographical, populational, or even individual) variability as taxonomic (specific) differenciation!

Jean-François Ponge, you raised a very interesting problem. Of course it is obvious that cryptic species are now trendy. All molecular taxonomist want to confirm their methods describing a species which are for classical taxonomists identical or almost identical. But discrimination of the species based on well defined molecular markers was confirmed in many studies.

If it were as you say, the observed changes / mutations would always be different, meanwhile we find very often the same haplotypes in different locations. This means that molecular method works well.

The other problem is if the species are really cryptic or we just not see differences in their morphology, sometimes due to imperfect methods of observation. In most of the cases we analyze only external morphology, ignoring completely internal morphology, physiology etc. Moreover we also ignore the fact that most of small invertebrates use a different methods of identification of thier self, for example a chemical traits, different spectrum of light etc.

There are several aspects of cryptic diversity and speciation.

First, we have to keep in mind that cryptic diversity may refer to the diversity of phylogenetic lineages at various stages of speciation. Many species are metapopulations composed of more or less isolated populations. This isolation may be more or less strict and may last from hundreds to thousands or even millions of years. With time, such populations may even become highly differentiated or even divergent (at the molecular level) but still may retain the potential to interbreed when the isolation ends. Thus, indeed we may observe completely different genetic pools but only experiments will show whether such populations will really interbreed. On the other side, we know that even species that are clearly different with respect to their morphology and even habitat, may interbreed occasionally and incorporate part of the genetic pool from the other species. There is an interesting paper about the origin of European bison that deals with such an issue (DOI: 10.1038/ncomms13158).

Second, a large part of the cryptic species is obviously cryptic from our, subjective, visually-biased, perspective. The species may really differ in their physiology, pheromone system, behaviour etc., or even in some morphological details that we haven't perceived so far... Sometimes the morphological differences become obvious after we find out coherent differences at the molecular level... On the other side, there are cases of morphospecies that do not differ at the molecular level (of course it concerns only the markers that were used).

Third, in taxonomy, species is a testable hypothesis. We always need to remember, that we may be wrong defining a particular species, doesn't matter whether based on morphology, DNA or both...

Concluding I believe, that we are still far from understanding of the nature of speciation and of species... But that's the beauty of being a scientist ;-)

Hello,

I am in agreemrnt with Michal Grabowski. He mentions good points about the discussed issue. He is totally right; the working field knowledge should become wider for our better comprehension of speciation to find the cryptic diversity and catural haracteristicsn. At that time we can accurately define our species.

Best, Elaheh

Cryptic species concept appeared when we try to shove a reality (which cold not be described by a single formula) to a universal dogma ("species concept") or local belief ("species hypothesis"). I see really "cryptic" species and pseudo-cryptic ones appeared due to a low resolution of the analysis, but I do not see difficulties due to this.

Many thanks for sharing your knowedge

From the above discussion I see that confirmation of cryptic speciation by experimental breeding experiments is mandatory. Unfortunately, this has been rarely achieved in the most recent researches on this topic. And, last but not least, I think that claiming for cryptic speciation within parthenogenetic species or lineages is a nonsense. However, nobody replied on that point, which is a pity. Many thanks to all of you for your clear and detailed responses.

To describe cryptic species traditional lines of evidence in taxonomy need to be modified. DNA sequence information, for example, could even serve as the backbone of a taxonomic description. The present contribution demonstrates that few adaptations are needed to integrate into traditional taxonomy novel diagnoses based on molecular data. The taxonomic community is encouraged to join the discussion and develop a quality standard for molecular taxonomy, ideally in the form of an automated final step in molecular species delineation procedures .

I attached the file for more information. Thank you respected sir, for your experience question.

doi: 10.1186/1742-9994-10-59

molecular methods, as DNA-barcoding could suggest many different species ever with no examination of the specimens. However, remain question, how we considerate "species" under this circumstages: morphology is only one of the aspects of the population diversification, as noticed Michal Grabowski. Gaps in DNA-barcoding analysis could indicate to the isolated grpups of individuals or populations, but it also could be effect of the material biases. So, only molecular data could be only one of the reference point in the seach of the new species. And comparison amond different aspects (physiologycal, etologycal, morphologycal) could provide more solid evidences to the species, in mean of genetiacally isolated units, diversification.

Thanks to Michael Loizides for this enlightening reply...

I think that traditional taxonomy is more effective; DNA Barcoding has become a simple and fast fashion. Nowadays young researchers compete to publish by considering only the molecular aspect that must be completed by an extensive and comparative evaluation of morphology, anatomy etc... Unfortunately in several articles, we found erroneous pictures of species originally studied. Reviewers of several accepted reputable publications should take this into account in order to keep alive the old faithful and accurate descriptive methods.

Hello everyone

A small contribution to the debate, in the form of a bibliographical reference. The reading of this publication (a little theoretical but with practical applications) seems to me quite enlightening...

Schlick-Steiner BC, Steiner FM, Seifert B, Stauffer C, Christian E, Crozier RH (2010) Integrative taxonomy: a multisource approach to exploring biodiversity. Annual Review of Entomology, 55, 421–438.

I fully support the Michal Grabowski's point of view and also the point of view and Michael Loizides. We need to develop more integrative taxonomy. Molecular tools are a good starting point but other kind of supporting information (morphology, distribution, physiology etc....) are mandatory. On the one side, we must avoid the fast food taxonomy but on the other side interbreeding tests are simply not possible for 99% of species. For those species, integrative taxonomy is a good starting point as suggested by Michal, species is just an scientific hypothesis that need to be confirmed or not. So Taxonomist and molecular ecologists need to collaborated to be built strong enough tools to solve this issue because Neither taxonomist nor Molecular ecologist have the all the truth. So, instead of to know who is the greatest, we need to cooperate by assuming that no one community have the good answer.

In my opinion, cryptic species do exist though sometimes they are no more than artefacts of machine analysis of genetic data. But it is inevitable today, when taxonomy is becoming the business of artificial intelligence :( By the way, the concept of cryptic species is much older than it is shown be Web of Science. As early as 1910, a Russian entomologist Nikolay Kholodkovskiy described morphologically cryptic but biologically different species of aphids (genus Chermes). Kholodkovskiy did not use the term "cryptic species", instead he named these entities "biological species" (do not confuse with "biological species" sensu Mayr). The recent advances in molecular taxonomy made the existence of cryptic species more evident, but their reality has been hotly debated in the 1940-1960s (see, for example, seminal monographs of Mayr).

Thank you Christophe Piscart . The commonest confusion I encounter is the labelling of coal, coal seam gas and petroleum reservoir species and their ecosystems as 'fossil fuels'. They are generally ancient living extremophile species. Possibly some of the oldest known.

Definitely not a specialist on the question, but ran into this paper by Daniel Fernandez Marchan that may contribute to the discussion:

Local adaptation fuels cryptic speciation in terrestrial annelids

https://www.sciencedirect.com/science/article/pii/S1055790320300397

Much of the cryptic species of Lepidoptera, and other insects orders, have a different bioecology and, sometimes, any taxotomic details used in the past to describe them as good species. I´m not DNA specialist, but i think that, in this case, machines are good tools to see clarely moments in the evolution process of speciation. The anatomic characters does not necesarely have to be manifested when two or more isolated populations return to be together, but now with differents genomic characters, and bioecology. To the human point of view, they are aparently the same thing, like the surface of Mars if we only look with ordinary optical cameras. But, with other technologies, like LIDAR or infrared, the surface of the planet is very different, and we can see other reality, and be abble to understand a little better the past and evolution of this world.

Distinct species are not distinct because of either morphological or molecular differences but because they are reproductively - and, consequently, evolutively - isolated, are segments of separate evolutionary lineages, so if morphology, bionomy, geography will not help in decision, DNA would be equally inconclusive!

In my estimation, if you have cryptic species you might not be looking closely enough.

What I've found in my investigations on some ticks and lacewings is that all species complexes or 'problems' that are taxonomically cryptic can be resolved into either distinct species or populations within a single species if you look closely at the 'correct' morphological feature. Often they are congruent with distinct lineages below the unoffical threshold of 95% genetic similarity that tend to mark distinct species in arthropods.

Using something like geometric morphometrics to rigorously characterise the shape of a particular morphological character among a set of organisms (including taxa closely related to the cryptic complex) is often able to detect subtle shape changes that would evolve due to drift after initial divergence.

However, this does mean choice of the character is important. My guess is that more complex shapes might be more susceptible to drift and indicate divergence better than simpler morphological shapes.

Ultimately, this approach considers that congruence between genes and morphology is important, but at a smaller scale than traditional methods can provide.

Comparing very close species, we always need to keep in mind that variability which we could observe from the field collected material (contrary to labobatory reared populations) is including interspecific component as well as geographycal (among populations) and phenotipycal. And in general situation, having only field material, we could not separate all these components. Thus, is cases with high intraspecific variability (in all means) could be that traits separating species completly are not exist. And each trait separatly give only probabylity to be corresponding to certain species. As observed in Encyrtus sasakii (Encyrtidae, Hymenoptera), divided into three species according host use, mating test, and COI divergence ( around 10% interspecific vs around 3% intra- ) By the other hand, molecular data as COI sequences not always separate close species, described on the morphologycal features. As in genera Limnebius (Hydraenidae, Coleoptera). In the second case each species (or al least form described like this) could be unambiguously identified according very variable and comple male genitalia shape.

I do not think cryptic species are erroneous creations of machines, but rather, flawed interpretations of data and uncritical application of the term that is not anchored on an evolutionary framework. Many studies claim to have uncovered hidden cryptic diversity by demonstrating high levels of genetic structure. Phylogenetic arrangements (distinct clades) and distance-based measures (e.g. p-distances) are further used to justify the distinctness of these cryptic lineages. However, genomic studies that examine gene flow and population-level processes are beginning to demonstrate that highly admixed populations can appear as distinct lineages with high genetic divergences. Conventional phylogenetic trees and distance-based methods are unable to disentangle the effects of gene flow and therefore have the potential to cause taxonomic inflation.

Article Gene flow creates a mirage of cryptic species in a Southeast...

The first argument, "if there is no phenotypic variety, then there must be interbreeding" is very dubious. What exactly is meant under the term "phenotype" here? If you mean some morphological and anatomical treats, which are traditionally used to delimit species within a macrotaxon, it is obvious that a lack of difference in these characters by no means guarantee the ability to interbreed. The incompatibilities leading to hybrid dysgenesis may be chromosomal, biochemical, physiological or behaviorial, thus invisible to morphology-based taxonomy.

Concerning the second argument, I do not completely understand it. Do you mean somatic mutations or PCR errors? Anyway, modern methods of species delimitation basing on DNA data have gone far away from judging basing solely on p-distances between selected mitochondrial markers. They include population analyses of nuclear markers, especially in contact zones. Thus, with molecular methods we are able to directly test whether there is interbreeding or not.

In reply to Artem Lisachov I must say that I do not find " "if there is no phenotypic variety, then there must be interbreeding" in my arguments, most probably this came from another contributor to the discussion, not me. What I meant was that genetic variation within species is a normal result of evolution, and has nothing to do with speciation until a barrier (whether geographical, ecological or behavioural) occurs among or within populations leading to potential interbreeding collapse. In a lot of studies claiming for the existence of cryptic speciation population analyses of the type you describe in your second paragraph are quite absent. In my rather provocative second argument against the validity of cryptic species I argued that PCR errors could mirror somatic mutations occuring through repeated mitoses, in particular in the presence of chromatin marks. Being an ecologist not involved in molecular taxonomy I cannot judge whether this is a result of my misknowledge of molecular methods of a true perception of methodological limits to theses methods. I am still in expectation of a clear assessment of what happens during enzymatic replication of DNA. Did somebody tried to compare what happens during DNA replication by PCR to the reproduction of somatic cells? I did not find that in published literature. Some references to articles or textbooks discussing that would be welcome...

So-called cryptic species, matching the generally accepted 97% rule appear in literature often within the framework of a rather limited study. My first question is then: did you see the whole range of variability of the species within its whole geographic distribution? Because often you see these patterns change when substantially more material is sequenced. In many cases such cryptic species appear to be variants within a wider species concept. I such cases I find it acceptable to have an substantial variation in ITS (or other genes) as well, even more than this 3%, particularly if this satisfies the need for a morphologically identifiable species. Several species recently described as new were introduced as being non cryptic because the authors indicate "good" morphological differences. With much more material, these good morphological differences may well appear to be gradual and overlapping. Are these species pairs now to be called cryptic? No, I do not think so, they better can be taken together as one variable species. I have for example the feeling the Neoboletus xanthopus and N. erythropus in many cases cannot be distinguished morphologcally, I have seen that in a number of own samples: are these then cryptic, or must we accept a much wider morphological concept of N. erythropus, and put xanthopus in the synonymy? A very different case of cryptic species I encounter in my current work on Entoloma (Basidiomycota, Agaricales) where you find species that are morphologically absolutely similar in different parts of the tree, so evidently not related and differing in dozens of base pairs. How to deal with those? You cannot put them together, like in sister species, so they need to be described separately, but cannot be identified without an ITS barcode. Are these true cryptic species, or do we need a new term for these?

Yes. Firstly cryptic species exist and a headache for taxonomists. But it seems obvious that DNA analysis is helpful when we cannot discriminate them just by observation. It is necessary, however, to examine their morphology or reproductive organ in detail first because even though they look the same we are supposed to find the difference any how, from my own experience. If it's the case with 'key character' the better. I don't think DNA method should come first.

I would say that for biodiversity study morphological study will be sufficient. But

when we need to differentiate them anyhow then DNA study matters.

Thanks for sharing your knowledge

Yes,the cryptic species exist.

To see the following Symposia:Cnidaria, from Latin American Congress of Marine Sciences-COLACMAR 2019. November 4-8,Mar del Plata,Argentina.

The paper "Cryptic species in Anthozoa:a hidden diversity by Antonio M.Solé-Cava.p.43.

A short response here is needed. Yes, cryptic species do occur, although they may not be as common as we think, depending upon our species definition and concept used. They are not distinguished easily unless one examines their ecology, ethology, biochemistry, physiology and most of all their molecular structure. My co-workers and I are in the process of publishing on a cryptic species in the subgenus Holothuria complex of species. We have managed to separate the two cryptic sympatric populations of one species using ossicle morphology and their morphometric data statistically analysed and gene sequencing and are in the process of describing a new species in the Holothuria (Holothuria) tubulosa complex. A real problem with cryptic species is that there are minute morphological details only observed after some morphometric study and gene sequencing. Both these are easily observable if detailed study whereas other aspects of their biology are not.

Dear Michael, your response is very clear and when I was writing my answer to the question I asked myself the same question, ie. if there are morphometric differences are they really cryptic, but neglected to take my thought any further. Therefore, I am in full agreement with you that they should be described as semicryptic. I think we will have to include this aspect in our MS which fortunately has not yet gone out for review. Once again thanks for your response. What happens if the two populations show only, say behavioural differences and not morphometric ones, besides those that are molecular, are not the two types then considered as truly cryptic

Dear Ahmed.

You said "what happens if the two populations show only,say behavioural differences and not morphometric ones,".

About it,I do the following comment:in 1979 I was studying taxonomy of sea anemones (Cnidaria:order Actiniaria) in Alberta University (Edmonton,Canada).During this study there was two sea anemone´s population,one of species Stomphia coccinea and another Stomphia didemon.From anatomical view both of them are equal and it is impossible to know each one.Only the swimming behaviour let to know each one,because each one has swimming responses differents when they are in contact with sea star (Echinodermata:Asteroidea).

So,my question is: the behaviour swimming is not enough for considering this two cryptic species?.

I think that behavioural differences between morphologically similar species are important if they prevent interbreeding, thereby resulting in a low degree of cross-fertilization, or even not at all. In other cases, the point is whether these species are living together or not. If they live together and show distinct behavioural patterns, this might indicate that full speciation (with genetic incompatibility) has probably already occurred. If they live in distinct areas but can interbreed when grown together they can be just a geographical segregation between populations of the same species (possibly ecotypes if the environment differs to some extent) or are faced to an incipient process of speciation. Anyhow, the whole discussion lets me in a great confusion about the criteria to be met for concluding to cryptic species. Given our methodological limits for discerning subtle morphological (or even more physiological or behavioural) differences, I think that discerning cryptic species by the use of molecular methods is just a step towards a better knowledge of the taxonomic status of a species, which has to be further confirmed by other methods, including interbreeding as an early assessment of the species status.

Hello all; Among host-specific parasites cryptic species seem to be common. Dan Janzen and his colleagues have worked extensively on the topic in the Neotropics. Here is the title of a pertinent example.

"Extreme diversity of tropical parasitoid wasps exposed by iterative integration of natural history, DNA barcoding, morphology, and collections" The paper is accessible at Google Scholar.

Best regards, Jim Des Lauriers

This is a very interesting question. I will answer it from the extreme point of view of cryptozoology and cryptobotany.

Cryptids (Greek κρύπτω - hidden) are animals or plants, the existence of which is considered possible by the supporters of the pseudosciences of cryptozoology and cryptobotany, but not recognized by academic science. A cryptid can be a creature that is considered extinct or that is described in legends, but about the existence of which there is eyewitness testimony. Usually, cryptids are understood as animals, since the existence of unproven plants is easier to confirm or deny. If you study the literature

Eberhart, George M. (2002). Mysterious Creatures: A Guide to Cryptozoology. Volume 2. Santa Barbara, CA: ABC-CLIO. ISBN 1-57607-283-5

Eberhart, George M. "Mysterious Creatures: Creating A Cryptozoological Encyclopedia." 2005. Journal of Scientific Exploration. Vol. 19, No. 1

It is clear that the question of mysterious species will always be the subject of scientific and pseudoscientific research.

Regards, Pushkin Sergey Viktorovich

Dear Jean-François Ponge To my knowledge, "cryptic species" and "cryptic diversity" both exists in natural populations. That what machines are creating today has been occurring in nature since beginning of the evolution.

Regards!

Thanks for the first answer, species concept is testable hypothesis (which enclosed the many concepts of species and cryptic species). I would like to add some theoretical sentences, cryptic species may be a common phase in speciation. Second, as we claimed that biodiversity is still largely unexplored (identified and described), because still almost all grps of organism are still documented with the help of morphology (in most cases that morphology is inadequate to describe a species). But the advent of barcoding or metabarcoding and DNA sequencing helping to uncover this great diversity. As already mentioned, cryptic diversity are determined at phylogenetic level during speciation, this concept is so powerful to explain evolution of species (what Darwin proposed). I think, as a junior scholar, we need a good set of methods and techniques and concepts to define a species, at least, in supportive and verified way as they living in nature.

Hello Barkat; To your last sentence... Natural populations' boundaries are evidently very messy. It is likely that in most taxa their genetic distinctiveness will never be clear. Large amounts of gene flow seems to be common and so selection will vary from one place to another and, as a result, strict reproductive isolation is unlikely. Best regards, Jim Des Lauriers

Barkat Ali , i also so publications were that "cryptic species" are interpret as a "proto species": according this population at the begining accumulating molecular diversification, and then - morphology. This could happend in cases of the allopatrical speciation, were is ecologycal diversification has minore rule in comparisone to the genetic isolation, which provides base of the diversification. But when speciation is based on the ecologycal specialisation and spatial isolation is only minor factor, geno- and phenotipical changes should be correlated more strictly., and cryptic species not will appear as a clear "proto" phase in the speciation. However, in examples, as i saw among Encyrtus lineages, it is seems that cryptic species there are common and clearly associated with the geographycal isolation. In cases like this "cryptic" character of speciation could be caused by the wide total variability and unstudied norm of reaction to environment, which could separate species, weather total variability from the field material is not.

Barkat: "in most cases that morphology is inadequate to describe a species" - in fact, just the opposite is true: in most cases only morphology (evtl. corroborated with analysis of reproductive isolation) is adequate to discover and describe species: "metabarcoding and DNA sequencing" can suggest, corroborate, or (when - as e.g. in some cases of allopatry or allochrony - morphological differences are undecisive and reproductive isolation cannot be directly tested) serve as a "proxy", but reliable determination of specific distinctness need the study of morphological variability and/or degree of hybridization (for more detailed argumentation please see e.g. the attached file!)!

Jean-François Ponge Hi Sir, thank you for the explanation at population level. However, this mess or puzzle in most of these populations luckily resolving using population genetics (e.g. SSR markers etc)....Sir, I think it should be customary to have full set of methods and concepts ? Your sincerely, Barkat

Andrey Rudoy Yes, nice observations in your study.....clearly diversification and speciation are driven by many processes and these processes might be accumulative or few or single with respect to taxa we studying.

Roman Bohdan Hołyński Thanks Sir, sure I'll take a look on it. Regards, Barkat

This super cool and interesting problem is another vivid reminder of how important is to support Taxonomists and Taxonomy across fields and disciplines. Especially in fast-growing fields such as the study of Biological Invasions:

Article Error Cascades in the Biological Sciences: The Unwanted Cons...

Thank you for sharing your knowledge

Hi.

In oceanic islands like the Canaries or the rest of the Macaronesian region (Azores, Madeira, Cape Verdes) there are many species which can be treated as "cryptic species", due to geographic isolation, low degree of taxonomic knowledge and recent application of modern techniques (mainly genetics and integrative taxonomy). In fact, there are several good examples of this in the last years, e.g. with plants, birds and reptiles. I can mention, between many others, two cases from the Canary Islands: Gran Canaria Blue Chaffinch (Fringilla polatzeki), separated from Tenerife Blue Chaffinch (F. teydea), and the skink Chalcides coeruleopunctatus, separated from C. viridanus, of which was a mere subspecies.

Best regards.

What about genome size? If we see within one taxon 2 peaks in the graph of the distribution of the amount of DNA, what is it?

Dmitriy Skorinov this could be polyploid species, generally these species have some clear differences each other and could not be cryptic species

Yes, cryptic species do exist. I discovered three cryptic species in the genus Philaethria, which are morphologically almost identical and present sympatric distribution, but when studying their biology in the field I found that they presented different flight behavior (vertical stratification), different host plants, different numbers of chromosomes, and they could not be crossed in the laboratory (reproductive isolation). The study of genetic crosses of populations in the field is more reliable to understand how genetic introgression works and not by means of a PCR that does not resolve differences in complex populations of a species. In molecular biology there are false positives that give rise to imaginary "species."

For this reason, taxonomy today must be integrative through studies of behavior, genetics, morphology, biogeography, hybridization and DNA analysis to understand the concept of "species" and not through a single analysis of a PCR machine. According to Ebach, M.C & Holdridge, C. 2005 barcoders maintain that there exist “DNA species” that are impossible to tell apart from known species except through sequence comparisons, many new species identified by barcoding would not be morphologically distinguishable. The resulting, much larger number of “species” would be a number that means very little. What that number might tell us about actually existing species would have to be intensively investigated, because barcodes cannot reveal the types of their corresponding real species, those species’ relationships, or their behavior.

Constantino's analysis is entirely compatible with that of Dan Janzen and his host-specific wasps. There appear to be a very large number of "species swarms" of this sort. Best regards, Jim Des Lauriers

The assignment of the ‘cryptic’ status, should then follow, but only after and independent from the species delimitation process. In this step, one should quantify morphological disparity. The status of ‘cryptic species’ should only be attributed if the species under consideration are morphologically more similar to each other than expected, given the time since species divergence.

Of course there are cryptic species. I have worked with fruit flies, mainly Anastrepha fraterculus and A. obliqua, in A. fraterculus genetic, cytogenetic, morphometric, mating and sexual incompatibility studies have been carried out, showing that it is a complex of cryptic species (6 morphotypes), Therefore, it is necessary to integrate different tools to determine the status of the cryptic species.

https://www.researchgate.net/publication/337301895_What_Can_Integrated_Analysis_of_Morphological_and_Genetic_Data_Still_Reveal_about_the_Anastrepha_fraterculus_Diptera_Tephritidae_Cryptic_Species_Complex/stats

https://zookeys.pensoft.net/article/6228/

https://www.eje.cz/pdfs/eje/2019/01/13.pdf

Totally agree with Michal Grabowski that species is a testable hypothesis in taxonomy, and also go along with Michael Loizides that cryptic species in most cases are merely the result of superficial or inadequate taxonomy. Given a species hypothesis following whatever species concept, a cryptic species means its boundary remains to be defined following whatever criteria pertaining to the relevant species concept, and a diagnosistic character yet to be discovered to distinguish its members from other species.

Hi Shi; As I commented earlier, there are host-specific parasite guilds that cannot be distinguished morphologically but are entirely reproductively isolated from one another. Sexually parasitic parthenogens in the fish genus Poecilia provide more examples. They are all perfectly good species by any of the prevailing definitions. Best regards. Jim Des Lauriers

In this case, the term cryptic species refers not only to the lack or scarce taxonomic depth to identify and separate these species, on the contrary it refers to evolutionary processes that have occurred within populations of the species due to different changes in the environment, as physical barriers, adaptation to different altitudinal ranges, and even to changes in the types of food (host plants) generating differences in reproductive behavior, genetic variations, morphometric changes, among other aspects that end up being relevant to be able to define the species status cryptic.

Good question! Cryptic speciation is a biological process that results in a group of species (which, by definition, cannot interbreed) that contain individuals that are morphologically identical to each other but belong to different species.

Ozodbek Abduraimov Jeferson Saavedra-Díaz . Thank you for your insightful answers.

I think it is kind of weakness of philosophical mind of many natural scientists in the world. In some parts of natural science fields (mathematics or many technological sciences) or some biological theories, we can justfy or draw the very crystal clear line between each concept or phenomenon. However, in ecology and/or zoology, we cannot put many things into boxes clear and clarrfy something. Namely, there are many grey zones between black and white. Therefore, we use statistics in order to show an evidence for something proportionally (Out of 95% confidence interval does not mean " it does not exist" But, it means, it is not general). Unfortunately, however, it still does not work well in our fields... Overall, I think some scientists want to be perfect too much so they become being very pedantic (sarcastic about making and find rules too much) too. That is why this kind of the situation happens.

Hi again.

More examples of cryptic species from the "Macaronesian" or Mid-Atlantic Islands are two new taxa of the family Campanulaceae from the Cape Verde Islands, described some years ago: Campanula hortelensis and C. feijoana. They are endemic to the island of Santo Antao and were confused with the species C. jacobaea, known from long time and endemic to several islands of the archipelago.

Evolution is based on the existence, formation and disappearance of cryptospecies. However, in the case of geographical speciation, this stage necessarily goes through the formation of an intermediate stage - geographical variety or race.There are also so-called phytochemical races of the same species as Juniperus oxycedris DC. The plants from the western part of the area synthesize radically different chemical compounds from those in the eastern range of the same species. Visible morphological difference does not exist.

If today, on the basis of classical morphographic criteria, it determines the exact number of plant species to be 315,000 species, of which at least 15,000 are not yet described, then with the introduction of new molecular criteria their number would increase to an incredible 2,000,000 plant species. . This includes all crypto species.

Just a few words to say that races of the same species, whether based on morphological or physiological or biochemical criteria (i.e. phenotypic variation) should not be considered as crypto-species. They are known and were described for a long time before the advent of modern molecular methods based on DNA. They belong to the common variation existing within or among populations of the same species. Other processes (geographical or ecological isolation, incompatibility of hybridation, hybrid sterility, etc.) are necessary to speak of species or at least of incipient speciation. Molecular methods may help suggesting races or ecotypes exist within species, better and more rapidly than classical methods, but do not attest for the existence of new species, whether called cryptic or else...

As experience has already shown, cryptic species are often only traditional ecological or/and geographical forms of species.

cryptic species barelly could be an ecologycal form due to they have no visible differences by the definition. At the contrary, ecologycal forms could be tested as one species by DNA similarity.

Differences can be subtle, i.e. presence/absence of a pair of setae on the thorax of a springtail. However, nobody can believe that physiological, phenological or behavioral differences are subtle. However, they escape totally to the anatomist...