Abstract
BackgroundMesoamerica is a remarkable region with a high geological and ecological complexity. Within northern Mesoamerica, the biotic province of the Sierra Madre del Sur (SMS) in southwestern Mexico harbors exceptionally high avian endemism and diversity. Herein, we searched for spatially and temporally concordant phylogeographic patterns, in four bird genera from three distinct avian orders co-distributed across Mesoamerica and investigated their causes through hypothesis testing regarding historical processes. Selected species include endemic and differentiated populations across the montane forests of Mesoamerica, and particularly within the SMS.ResultsWe gathered mitochondrial DNA sequences for at least one locus from 177 individuals across all species. We assessed genetic structure, demographic history, and defined a framework for the coalescent simulations used in biogeographic hypothesis testing temporal and spatial co-variance. Our analyses suggested shared phylogeographic breaks in areas corresponding to the SMS populations, and between the main montane systems in Mesoamerica, with the Central Valley of Oaxaca and the Nicaragua Depression being the most frequently shared breaks among analyzed taxa. Nevertheless, dating analyses and divergence patterns observed were consistent with the hypothesis of broad vicariance across Mesoamerica derived from mechanisms operating at distinct times across taxa in the SMS.ConclusionsOur study provides a framework for understanding the evolutionary origins and historical factors enhancing speciation in well-defined regions within Mesoamerica, indicating that the evolutionary history of extant biota inhabiting montane forests is complex and often idiosyncratic.
Highlights
Mesoamerica is a remarkable region with a high geological and ecological complexity
These differences may be due to the fact that both taxa inhabit different elevational ranges along the region: Eupherusa ranging to the lower limits of the cloudforest and Cardellina ranging in the upper reaches of the humid montane forest, suggesting that isolation and connectivity cycles in the vegetation types might have a differential impact on the genetic pool of birds depending on the elevational range, which might explain the observed patterns [74]
For the C. rubra lineage the observed strong signature of expansion in Trans-Mexican Volcanic Belt (TMVB) and Sierra Madre del Sur (SMS) populations due to Pleistocene conditions and forest migrations resulted in the admixture of two isolated lineages; our results reveal that demographic dynamics for other species persisted in isolated regions throughout the Pleistocene allowing the evolution of high endemism, which could be an overall result of high effective population sizes
Summary
Mesoamerica is a remarkable region with a high geological and ecological complexity. Within northern Mesoamerica, the biotic province of the Sierra Madre del Sur (SMS) in southwestern Mexico harbors exceptionally high avian endemism and diversity. Rocha-Méndez et al BMC Evolutionary Biology (2019) 19:237 complex geological history of this region, as well as the cyclic changes in vegetation and climate, pose it as a challenging area for biogeographic and evolutionary studies; in addition, constant orogenic processes have promoted a highly broken topography characterized by highland isolated patches of humid montane forest between 600 and 3000 m, which includes both humid pine-oak forest and cloud forest [22,23,24] This mosaiclike landscape has been associated to centers of diversification along elevational gradients, in which both a high species richness and endemism have evolved for the last 2 Myr, likely as a result of both environmental and geological complexity, as well as Pleistocene climatic fluctuations [6, 15, 18, 22, 25,26,27,28,29], which is supported by relatively recent intraspecific differentiation processes in several groups of organisms (see [27, 30]), explaining the existence of numerous endemic species in different taxonomic groups, including birds [31,32,33,34,35]. As in other Mesoamerican bird taxa [44,45,46,47,48], the SMS holds endemic and well-differentiated subspecies, suggesting the importance of isolation for the evolution of intraspecific variation [17, 49]
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