I don't do research on this subject myself, but during my studies I read something that might be relevant. It seems that close to the poles there is a higher percentage of polyploid plants and more vegetatively propagated plants than in tropical regions. This might have something to do with the requirement for long-term stability of genotypes. A plant in polar regions should not change its genotype too quickly if there are a few milder winters, because it needs to remain able to survive the severe winters that will inevitably follow. In tropical regions it might be an advantage to immediately adapt to any niche that becomes available. If that's true, you should also suspect more self pollinators than cross pollinators in polar regions. So if you look at distribution of dioecy, it might be interesting to look at these aspects as well.

I am doing studies on dioecious Moraceae, specifically on two genera of trees, Morus and Maclura. My research started with finding significantly higher levels of phytoestrogen activities of female extracts than male extracts and continued with studying the sexual dimorphism of these trees. Since Morus is practically found in both temperate and tropics-subtropical climates, it would be interesting to see geographical differences. If you are interested in Morus alba, for example, we can try to collaborate. You can look me up on ResearchGate but I also have results which have not yet been published. You can write to me at [email protected].

I wonder if it may be related to the proportional increase in animal versus wind pollination form the poles to the tropics?  See the first paper below. 

I may be potentially interested in collaborating with you on this, it's an interesting question and I have worked on some dioecious species (see second paper).

Article How many flowering plants are pollinated by animals? Oikos

Article Phenotypic selection on flowering phenology and size in two ...

Dear Zheng JingMin: You may already know about Dr. Wang Juan's work on dioecious Rhamnus. She is a young teacher at your university . If not, here are two recent studies. Good luck and best wishes. Klaus Gadow

We are working on sea buckthorn in Ladakh region, which a dioecious with xy sex determination.

Thanks Jeff. It is an interesting way to look into the pattern.

Can I ask how to determine the type of pollinator for plant species for sure? I realize this information, as well as size of flower, color, and fruit type, might related with sex system type, however, I could not find pollination vector for most of the species from flora books. maybe it is not a problem for you?

I have follow you up in ResearchGate.

Determining the effective pollinators of a plant is not at all straightforward, particualrly for plants with small flowers and/lots of different types of flower visitor.  You have to bag flower buds before they open, then expose the virgin flowers to single visits by each type of visitor, with appropriate sample sizes and controls.  I've linked to an example below.

If you mean determining if it's wind or animal pollinated, that's a bit more straightforward: wind pollinated plants tend not to invest resources in large corollas, colour pigments, nectar, or scent, though there are exceptions.  Also if you shake wind pollinated flowers in dry, warm conditions, you usually see clouds of pollen being released. 

Article Pollinator effectiveness of native and non‐native flower vis...

thanks everyone for the concerns.

Still another small question: how to determine the climatic distribution status of a plant species? generally, there are three category,i.e., temperate, subtropical, tropical. however, some species may distributed across two climate zone, say, temperate and subtropical, is it ok to classified this plant species as subtropical species? how to use Koeppen climate system to help this? 

any idea is welcomed!

It would be best to base the data on field surveys, then it's the population that can be classified or (better) geo-referenced.

 Dear Jingming Zheng,

If it is still actual, I know a scientist who have studied dioeciuos species in Carpathian mountains in West Ukraine (principally in Ukrainian). Perhaps, she can calculate them , the Carpthians flora is well known. I like your global question, I have the similar question on fruits.

bioweb.lnu.edu.ua/studia/pdf/201373/2013_7_3_285.pdf

Hi Dr. Odintsova,

yes, it is still active. you and your friends are welcomed to collaborate. Maybe we can find some ways to work it out. what are you suggesting?

only one problem, I don't read Russian,  sorry.

Jingming Zheng

BJFU, CHINA

I'll speak with her in a week. she most likely, write only in Ukrainian, if she calcule dioecious species in Carpathians flora, I can write some English text. I suppose it will be better to compare mountains with mountains or plain with plain. Life form and taxonomy are also important.  I give you know our propositions.

ok. let's try it.

frankly, I don't know too much about Carpathian flora, however, I can google and learn more

Dear Dr. Zheng,

I have a talk and obtain positive position on the collaboration about dioecious plants in Carpathians. There are some Ukrainian publications, where the number of dioecious species was estimated in 5-7%, monoeciuos - ca15%, hermaphrodites - 70-78% in the Ukrainian  Carpathians. There is also Gymnosperms/Angiosperms, Trees/Grasses and Dicots/Monocots analysis available.  I can write you more data on e-meil. My address is [email protected]