Dear Benjamin,

many thanks for this interesting question! Generally speaking, my answer would be a clear "yes". Short-term climatic variability as well as long-term climate changes (such as climate regime shifts, but also many other modes of climatic change) certainly influence competition within and between tetrapod species. I am thinking, for example, about species ranges and resource competition, but also many other factors and processes. You raise the issue of islands. Without doubt, tetrapod competition can be expected to be heightened within the unique frames of island ecosystems, especially on small- and medium-sized islands. However, could you further elaborate on what precisely you are referring to by "North-South cline"? Would be very interesting to know what specifically you have in mind there...

Thanks & best wishes,

Julius

Dear Julius,

Many thanks for your answer! Tackling insular ecological issues needs a deep understanding of processes taking place there as everything is intricated... What I meant by 'North-South cline' is the following: let's say we have the same species pool that would migrate to the same islands, which that are aligned along a N-S cline with a gradual change in climatic conditions (warm, humid at 0° of latitude towards cold and dry at 90° of latitude, to make it easier to handle). Would the final species pools on the different islands be a function of the local climate acting on a local island?

As you already noted, such differences would affect competition notably, on top of the differential ressource availibilities under different climates.

Thank you a lot for you interest!

Best regards, Benjamin

Dear Benjamin,

many thanks for getting back on this as well as for your explanations! Alright, I now understand your thought experiment much better and shall take on your challenge :-) But let me hasten to say that I am not an expert on Mesozoic tetrapods (as you probably are). My work focusses on climate impact research and evolutionary dynamics (on much different scales than yours), so I'll answer your question from that perspective: If the islands along the chain you are envisioning do indeed display different climate regimes (perhaps even lying in different climate zones) - and hence show different natural environments and ecologies - I am pretty sure that climate will constitute a co-driver of the composition and other properties of the "final species pool" (as you put it). However, I would like to emphasize the important qualification "CO-driver", by which I mean that various other factors of the insular natural environments as well as unpredictable "historical chance" will likewise be drivers of the resulting species pool. So I guess it will always be analytically very difficult to tease apart the influence of climate from that of all other drivers involved. That, by the way, is a challenge we encounter in climate impact research day in and day out... But I'd be interested to know whether you have any empirical case study at hand you want to apply these thoughts to? Like data on species or population pools in different insular settings? Mesozoic climates as well as configurations of continental landmasses were obviously very different from today and experienced a lot of changes over those ca. 200 million years - I don't know how highly resolving the palaeontological data sets are and whether they allow for such a fine-grained analysis in terms of spatio-temporal scales.

Looking forward to learning more about the data/research setting behind your question!

Thanks & best wishes,

Julius

Dear Julius,

Sorry for the late reply, I have been very busy the few last weeks. Many thanks for your last response. My thinkings are mostly theorical at the moment, but I hope to expand them to specific, quantified data in a close future.

Many thanks again for your help! Benjamin

Thanks for that, Benjamin! Yes, please do let me know should you be coming up with some specific data, case studies or the like! I am always interested in connecting climatic changes to evolution - especially if relating to island biogeographies :-) Thanks & best wishes, Julius