Ecomorphological trajectories of reef fish sister species (Pomacentridae) from both sides of the Isthmus of Panama

Abstract

The vicariance model of biogeography focuses on allopatric speciation through fragmentation from an ancestral biota via a barrier that interrupts gene flow between populations. The evolutionary processes that occur over time in sister species on each side of the vicariance event influence their traits by a compromise between divergence and conservatism. The eastern Pacific and the Caribbean Sea were separated by the Isthmus of Panama ~ 3-6 Mya and allopatric speciation occurred on either side of the isthmus. Differences in ecological conditions on each side of the Isthmus of Panama separating the sister species may have shaped their niches and morphologies over evolutionary time. The objectives of this study were to: (1) analyze the variation in niche, morphology, and size in each pair of sister damselfish species on both sides of the Isthmus of Panama, (2) determine whether these variables show specific patterns on each side of the isthmus, and (3) determine whether these variables are correlated through evolution. The results showed no relationship between morphology and niche, however, size was related to both niche and morphology. Sister damselfish species on either side of the Isthmus of Panama differ in terms of niche, morphology, and size. Nevertheless, they also show similarities, indicating environmental constraints and conservatism. This study describes a model in which adaptation or divergence and conservatism shaped the evolution of sister damselfish species on both sides of the Isthmus of Panama. These mechanisms are fundamental to population biology, and they act in opposite directions.

Functional diversity in fish assemblages of the Tropical Eastern Pacific Ocean: A review of two decades of progress in the functional diversity approach

“…It is hypothesized that the presence of a marine Pleistocene gap in the area of Panama (1.8-2 mya), initiated the divergence of some transisthmian species of the genus Anisotremus (Tavera-Vargas, 2006). While 85% of the coastal fish fauna of the TEP is derived from taxa present before the rising of the Isthmus of Panama, the low percentage of common species in the two regions of the American continent (> 100 sister species, pairs or transisthmian; see Table 4) is the result of independent evolution of their faunas in very different environments (Rosenblatt, 1967;Robertson et al, 2004;Aguilar-Medrano, 2018). In some genera, the sister species have been separated taxonomically by minor morphological differences or genetic differences, such as the Pacific machete and Atlantic ladyfish (Elops affinis Regan 1909 -E. saurus Linnaeus, 1766), Pacific sleeper and bigmouth sleeper (Gobiomorus maculatus (Gunther,1859) -G. dormitor Lacepede, 1800), the Pacific fat sleeper and fat sleeper (Dormitator latifrons (Richardson, 1844) -D. maculatus (Bloch, 1792)), Atlantic and Pacific spadefish (Chaetodipterus faber (Brousonnet, 1782) -C. zonatus (Girard, 1858)), the Panamic banged blenny and the red-lip blenny (Ophioblennius steindachneri Jordan & Evermann, 1898-O.…”