Animating geophylogenies: fish and fire

The Trans-Mexican Volcanic Belt is a mountain range that has developed over the last 15 million years, which runs east-west across central Mexico . As the name suggests, the region is highly geologically active, with large-scale tectonic uplift, frequent volcanic eruptions, stratovolcanoes rising to over 5000m, and frequent earthquakes and faulting. This activity, combined with erosive river capture and changing rainfall, resulted in wide-spread hydrological change including the development of large lakes in the Pliocene and Pleistocene. (5.4-2.4 Mya).

15 million year or so ago the ancestor the Goodeidae freshwater fish family was caught up in this dynamic landscape as it migrated south from the southwest USA with a drying climate.The 40-odd species of Goodeidae alive today co-evolved with the hydrological landscape, which itself is the product of geological and climatic forces. Each hydrological event could split a species' range causing it to diversify into two (allopatic speciation), while in the lakes sympatric speciation involving ecological and behavioural diversification may have occurred.

I have information on species distributions and the evolutionary relationships between species, geological data and partial hydrological reconstructions. How can this information be brought together to help construct a single history from the fragmented parts?

The animation took me a couple of days to put together in ArcMap. It shows gaps (disjunctions) and marginal overlap (<50%) geophylogeny built with GeophyloBuilder for ArcGIS 1.1 from a time-scale molecular tree (Webb et al. 2004) and species records (from Dr. Constantino Marcias Garcia, UNAM). Gaps and marginally overlapping polygons are displayed from orange (disjunct) to grey (50% overlap). The node associated with each DAVA polygon and its daughter branches are shown as black dots and red arrows (pointing downstream). This biological pattern overlays some palaeo-channel, lake and watershed reconstructions (de Cserna & Alvarez 1995), and the spatiotemporal pattern of extrusive volcanics (pink; from Luca Ferrari, UNAM). The Colima graben, which the palaeolake may have drained through, is shown in purple.

The animation ends with all branches of the geophylogeny being displayed, the width of the downstream arrows being negatively proportioned to age (thin = old). The temporal scale is roughly 16 million years from start to end with the biogeographic pattern displayed by the dates from the phylogeney and the volcanics by their stratgraphic range. The temporal extent of the hydrological reconstructions has been visually set to maximise congruence with the biogeographic pattern.

What does it show? Well, disjunction and marginal overlap between the DAVA polygons indicate where a species' range may have been split in the past, resulting in speciation. The arrows point to the centroid of where the daughter clade ranges are today. Some events are congruent with change in the hydrological network and the pattern of volcanism, others remain unexplained but suggest regions where hydrological change may have occurred in the past.

References

de Cserna Z, Alvarez R. Quaternary drainage development in Central Mexico and the threat of an environmental disaster: a geological appraisal. Environ. Eng. Geosci. 1995 1: 29-34.

Webb SA, Graves JA, Marcias-Garcia C, Magurran AE, Ó Foighil D, Ritchie MG. Molecular phylogeny of the live-bearing Goodeidae (Cyprinodontiformes). Mol. Phylogenet. Evol. 2004 30: 527-544.