Genetic and morphometric divergence in the Garnet-Throated HummingbirdLamprolaima rhami(Aves: Trochilidae)

Abstract

Cloud forests are one of the most endangered ecosystems in the Americas, as well as one of the richest in biological diversity in the world. The species inhabiting these forests are susceptible to environmental changes and characterized by high levels of geographic structure. The Garnet-Throated Hummingbird, Lamprolaima rhami, mainly inhabits cloud forests, but can also be found in other habitats. This species has a highly restricted distribution in Mesoamerica, and five disjunct regions have been delimited within the current geographic distribution of the species from Mexico to Honduras. According to variation in size and color, three subspecies have been described: L. r. rhami restricted to the Mexican highlands and Guatemala, L. r. occidentalis distributed in Guerrero (Mexico), and L. r. saturatior, distributed in the highlands from Honduras and El Salvador. We analyzed the levels of geographic structure in L. rhami and its taxonomic implications. We used mitochondrial and nuclear DNA to analyze genetic variation, demographic history, divergence times, reconstructed a multilocus phylogeny, and performed a species delimitation analyses. We also evaluated morphological variation in 208 specimens. We found high levels of genetic differentiation in three groups, and significant variation in morphological traits corresponding with the disjunct geographic populations. L. rhami presents population stability with the highest genetic variation explained by differences between populations. Divergence time estimates suggest that L. rhami split from its sister group around 10.55 million years ago, and the diversification of the complex was dated ca. 0.207 Mya. The hypotheses tested in the species delimitation analyses validated three independent lineages corresponding to three disjunct populations. This study provides evidence of genetic and/or morphometric differentiation between populations in the L. rhami complex where four separate evolutionary lineages are supported: (1) populations from the Sierra Madre Oriental and the highlands of Oaxaca (rhami), (2) populations from the highlands of Guerrero (occidentalis), (3) populations from the highlands of Chiapas and Guatemala (this is a non-previously proposed potential taxon: tacanensis), and (4) populations from the highlands of Honduras and El Salvador (saturatior). The main promoters of the geographic structure found in the L. rhami complex are likely the Isthmus of Tehuantepec as a geographic barrier, isolation by distance resulting from habitat fragmentation, and climatic conditions during the Pleistocene.

The geography of evolutionary divergence in the highly endemic avifauna from the Sierra Madre del Sur, Mexico

“…Our study also indicates that at least two unrelated bird genera ( Aulacorhynchus & Chlorospingus ) with distinct natural histories but which inhabit roughly the same regions and wide elevational range along the humid montane forests of Mesoamerica, present highly similar phylogeographic structure, including a significant split between the highlands in Guerrero and Oaxaca within the SMS, which may be expected due to discontinuous distribution ranges, as well as to their presumably reduced dispersal abilities. The pattern observed in Cardellina and Eupherusa do not fully agree with the expectation that the degree of isolation between montane ranges is responsible for shaping the genetic differentiation between populations, as has been reported in previous studies of montane birds (see [45, 75]). The analyses in these two taxa evidenced exclusive haplotypes from Oaxaca, but genetic differentiation across the Río Verde drainage, as seen in Aulacorhynchus and Chlorospingus does not occur.…”

“…We observed major breaks, as seen in Aulacorhynchus and Chlorospingus , between Chiapas and Mexican-Central American lineages. This has been also supported by other bird species [75], plants [18], rodents [20, 35], insects [51] and a snake [78]. Moreover, phylogeography shows isolation between populations inhabiting the mountains of southwestern Mexico (SMS) and northern Oaxaca (see Chlorospingus ) evidencing that populations are clearly sorted within Oaxaca across its Central Valley, and more importantly morphological variation of these populations has also been documented as in E. eximia nelsoni [79].…”

The geography of evolutionary divergence in the highly endemic avifauna from the Sierra Madre del Sur, Mexico

“…Our study also indicates that at least two unrelated bird genera (Aulacorhynchus & Chlorospingus) with distinct natural histories but which inhabit roughly the same regions and wide elevational range along the humid montane forests of Mesoamerica, present highly similar phylogeographic structure, including a significant split between the highlands in Guerrero and Oaxaca within the SMS, which may be expected due to discontinuous distribution ranges, as well as to their presumably reduced dispersal abilities. The pattern observed in Cardellina and Eupherusa do not fully agree with the expectation that the degree of isolation between montane ranges is responsible for shaping the genetic differentiation between populations, as has been reported in previous studies of montane birds (see [42,121]). The analyses in these two taxa evidenced exclusive haplotypes from Oaxaca, but genetic differentiation across the Río Verde drainage, as seen in Aulacorhynchus and Chlorospingus does not occur.…”

The geography of evolutionary divergence in the highly endemic avifauna from the Sierra Madre del Sur, Mexico

“…with distinct natural histories and which inhabit roughly the same regions in the humid montane forests of Mesoamerica, present highly similar phylogeographic structure, including a significant split between the highlands in Guerrero and Oaxaca within the SMS, which may be expected due to discontinuous distribution ranges, as well as to their presumably reduced dispersal abilities. The pattern observed in Cardellina and Eupherusa do not fully agree with the expectation that the degree of isolation between montane ranges is responsible for shaping the genetic differentiation between populations, as has been reported in previous studies of montane birds (see [42,121]), analyses in these two taxa evidenced exclusive haplotypes from Oaxaca, but genetic differentiation across the Río Verde drainage, as seen in Aulacorhynchus and Chlorospingus does not occur. Regarding Cardellina, despite the fact that the TMVB and the SMS montane ranges are separated by a significant geographic barrier such as the Balsas Depression (see [7]), incomplete lineage sorting between both regions is reported.…”

“…We observed major breaks, as seen in Aulacorhynchus and Chlorospingus, between Chiapas and Mexican-Central American lineages. This has been also supported by other bird species [121], plants [28], rodents [18,34], insects [48] and a snake [124]. Moreover, phylogeography shows isolation between populations inhabiting the mountains of south-western Mexico (SMS) and northern Oaxaca (see Chlorospingus) evidencing that populations are clearly sorted within Oaxaca across its Central Valley, and more importantly morphological variation of these populations has also been documented as in E. eximia nelsoni [125].…”