Systematics and conservation of an endemic radiation of Accipiter hawks in the Caribbean islands

Abstract

More than one-third of the bird species found in the Caribbean are endemic to a set of neighboring islands or a single island. However, we have little knowledge of the evolutionary history of the Caribbean avifauna, and the lack of phylogenetic studies limits our understanding of the extent of endemism in the region. The Sharp-shinned Hawk (Accipiter striatus) occurs widely across the Americas and includes 3 endemic Caribbean taxa: venator on Puerto Rico, striatus on Hispaniola, and fringilloides on Cuba. These island populations have undergone extreme declines presumably due to ecosystem changes caused by anthropogenic factors, as well as due to severe hurricanes. Sharp-shinned Hawks, in general, and Caribbean Sharp-shinned Hawks, in particular, have not been placed in a modern phylogenetic context. However, the island taxa have historically been presumed to have some ongoing gene flow with mainland populations. Here we sequenced ultraconserved elements (UCEs) and their flanking regions from 38 samples, focusing on Caribbean taxa. Using a combination of UCEs, mitochondrial genome sequences, and single-nucleotide polymorphisms, we investigated the phylogenetic relationships among Caribbean lineages and their relationships to mainland taxa. We found that Caribbean Sharp-shinned Hawks are reciprocally monophyletic in all datasets with regard to mainland populations and among island taxa (with no shared mtDNA haplotypes) and that divergence in the NADH dehydrogenase 2 gene (ND2) between these mainland and island groups averaged 1.83%. Furthermore, sparse non-negative matrix factorization (sNMF) analysis indicated that Hispaniola, Puerto Rico, and mainland samples each form separate populations with limited admixture. We argue that our findings are consistent with the recognition of the 3 resident Caribbean populations as species-level taxa because nuclear and mitochondrial genetic data indicate reciprocal monophyly and have species-level divergences, there is no sharing of mitochondrial haplotypes among or between island taxa and those on the mainland; and they are diagnosable by plumage.

The World's Most Imperiled Raptors Present Substantial Conservation Challenges

“…data). Recent genetic and morphological analyses suggest that this taxon should be considered a species (Catanach et al 2021). Given the rarity of the Puerto Rican Sharp-shinned Hawk and its drastic population decline due to Hurricane Maria (Gallardo and Vilella 2017), this taxon would likely be listed as critically endangered if considered a species.…”

Enigmas no longer: using Ultraconserved Elements to place several unusual hawk taxa and address the non-monophyly of the genusAccipiter(Accipitriformes: Accipitridae)

“…For our target sequences, we selected hawkspecific versions of the probes in the 5k tetrapod probe set. We used the Phyluce pipeline (Faircloth, 2016) to assemble UCEs from several high-quality hawk tissue samples, and then selected the longest representative of each UCE to serve as a target sequence for UCE assembly for other species in the study (Catanach et al, 2021). Using these targets, we then performed five iterations of BLAST queries against each shard (created by partitioning a large dataset into several smaller datasets to ease computational requirements).…”

“…The taxa in greatest need of additional sampling include the Accipiter poliogaster, various monotypic eagle genera, Pseudastur, and Rupornis magnirostris. Several species within Accipitridae are not monophyletic and a detailed revision of species limits within several clades is sorely needed (e.g., Catanach et al, 2021).Divergence time estimates may also be further refined (e.g., by including more fossil calibrations, and identifying datable biogeographic splits).…”

“…In other bird groups, higher level relationships have been largely resolved by sequencing large numbers of genes, either via genome reduction methods (e.g., Ultraconserved Elements, UCEs) or mining data from whole genome sequencing (Prum et al, 2015;Chen et al, 2021;Hruska et al, 2023). These methods also enable the use of degraded and highly fragmentary samples, like the toepads of study skins (e.g., Catanach et al, 2021), whereas Sanger sequencing often requires high quality DNA from fresh or frozen tissue. This is an important breakthrough for studies of Accipitridae systematics because high-quality tissues are lacking for several genera, due to challenges associated with collecting diurnal birds of prey (e.g., heightened legal protection and low population densities).…”

The taxonomic basis of subspecies listed as threatened and endangered under the endangered species act

“…Vaźquez-Miranda et al (2017) show that subspecies of the LeConte's thrasher (Toxostoma lecontei) found in the Vizcaino Desert of Baja California, and populations to the north, are genetically distinct and qualify as units worthy of conservation status. Catanach et al (2021) provide a textbook example of how a subspecies should be tested with modern methods. They examined the status of the hawk Accipter straitus venator from Puerto Rico using ultra-conserved elements (nuclear DNA), mitochondrial DNA (mtDNA), and morphology.…”