Evolutionary patterns and processes in the radiation of phyllostomid bats

Abstract

BackgroundThe phyllostomid bats present the most extensive ecological and phenotypic radiation known among mammal families. This group is an important model system for studies of cranial ecomorphology and functional optimisation because of the constraints imposed by the requirements of flight. A number of studies supporting phyllostomid adaptation have focused on qualitative descriptions or correlating functional variables and diet, but explicit tests of possible evolutionary mechanisms and scenarios for phenotypic diversification have not been performed. We used a combination of morphometric and comparative methods to test hypotheses regarding the evolutionary processes behind the diversification of phenotype (mandible shape and size) and diet during the phyllostomid radiation.ResultsThe different phyllostomid lineages radiate in mandible shape space, with each feeding specialisation evolving towards different axes. Size and shape evolve quite independently, as the main directions of shape variation are associated with mandible elongation (nectarivores) or the relative size of tooth rows and mandibular processes (sanguivores and frugivores), which are not associated with size changes in the mandible. The early period of phyllostomid diversification is marked by a burst of shape, size, and diet disparity (before 20 Mya), larger than expected by neutral evolution models, settling later to a period of relative phenotypic and ecological stasis. The best fitting evolutionary model for both mandible shape and size divergence was an Ornstein-Uhlenbeck process with five adaptive peaks (insectivory, carnivory, sanguivory, nectarivory and frugivory).ConclusionsThe radiation of phyllostomid bats presented adaptive and non-adaptive components nested together through the time frame of the family's evolution. The first 10 My of the radiation were marked by strong phenotypic and ecological divergence among ancestors of modern lineages, whereas the remaining 20 My were marked by stasis around a number of probable adaptive peaks. A considerable amount of cladogenesis and speciation in this period is likely to be the result of non-adaptive allopatric divergence or adaptations to peaks within major dietary categories.

Ecological variation in South American geophagine cichlids arose during an early burst of adaptive morphological and functional evolution

“…Our analyses, as well as that of Ló pez-Fernández et al [18] indicate that Geophagini underwent a mid to Late Cretaceous burst of functional evolution that was associated with the advent of modern ecological groups. In addition to geophagine cichlids, early bursts of morphological evolution have been observed in continental-scale radiations of furnariid birds [12] and phyllostomid bats [57] within the Neotropics alone, as well as within the globally distributed Cetacea [33]. Together, these patterns suggest that it is possible that models of evolution consistent with adaptive radiation are applicable to patterns of diversity and disparity on a broad geographical scale and encompassing long evolutionary times.…”

Phylogenetic fields of species: cross-species patterns of phylogenetic structure and geographical coexistence

“…Some stenodermatine species coexist with less related species. This could potentially result from either a dominant role of allopatric speciation followed by dispersal and convergent environmental preference among distantly related stenodermatines [44,45] or even geographical exclusion of closely related species [9]. Interestingly, the latter possibility may suggest that ecological sorting processes could be acting at larger scales [19].…”

“…This would allow them to occur at the same regions and coexist with closely and distantly related species, producing phylogenetic fields indistinguishable from range size variation alone. In fact, recent phylogenetic analyses suggest phenotypic and ecological stasis after early species' differentiation within Phyllostomidae followed by increasing speciation rates [44,51,52], which may account for the high number of closely related coexisting species. Finally, we cannot discard the potential effect of evolutionary range dynamics on current coexistence patterns [43,53], which may explain the lability and lack of phylogenetic signal in phyllostomid range sizes.…”

Roosting Ecology of Amazonian Bats: Evidence for Guild Structure in Hyperdiverse Mammalian Communities

“…Studies of phyllostomid adaptive radiation have hitherto focused exclusively on feeding behavior (e.g., Wetterer et al, 2000;Datzmann et al, 2010;Monteiro and Nogueira, 2011;Dumont et al, 2011;Rojas et al, 2011), resulting in scenarios that are sometimes accompanied by impressive analyses of trophic morphology. Although dietary adaptations have almost certainly played an important role in phyllostomid evolution, causal inferences in this literature would be strengthened if alternative behavioral traits that might also have influenced relevant evolutionary phenomena were considered.…”