Nuclear and mtDNA phylogenetic analyses clarify the evolutionary history of two species of native Hawaiian bats and the taxonomy of Lasiurini (Mammalia: Chiroptera)

<div><p>Previous studies on genetics of hoary bats produced differing conclusions on the timing of their colonization of the Hawaiian Islands and whether or not North American (<i>Aeorestes cinereus</i>) and Hawaiian (<i>A</i>. <i>semotus</i>) hoary bats are distinct species. One study, using mtDNA COI and nuclear Rag2 and CMA1, concluded that hoary bats colonized the Hawaiian Islands no more than 10,000 years ago based on indications of population expansion at that time using Extended Bayesian Skyline Plots. The other study, using 3 mtDNA and 1 Y-chromosome locus, concluded that the Hawaiian Islands were colonized about 1 million years ago. To address the marked inconsistencies between those studies, we examined DNA sequences from 4 mitochondrial and 2 nuclear loci in lasiurine bats to investigate the timing of colonization of the Hawaiian Islands by hoary bats, test the hypothesis that Hawaiian and North American hoary bats belong to different species, and further investigate the generic level taxonomy within the tribe. Phylogenetic analysis and dating of the nodes of mtDNA haplotypes and of nuclear CMA1 alleles show that <i>A</i>. <i>semotus</i> invaded the Hawaiian Islands approximately 1.35 Ma and that multiple arrivals of <i>A</i>. <i>cinereus</i> occurred much more recently. Extended Bayesian Skyline plots show population expansion at about 20,000 years ago in the Hawaiian Islands, which we conclude does not represent the timing of colonization of the Hawaiian Islands given the high degree of genetic differentiation among <i>A</i>. <i>cinereus</i> and <i>A</i>. <i>semotus</i> (4.2% divergence at mtDNA Cytb) and the high degree of genetic diversity within <i>A</i>. <i>semotus</i>. Rather, population expansion 20,000 years ago could have resulted from colonization of additional islands, expansion after a bottleneck, or other factors. New genetic data also support the recognition of <i>A</i>. <i>semotus</i> and <i>A</i>. <i>cinereus</i> as distinct species, a finding consistent with previous morphological and behavioral studies. The phylogenetic analysis of CMA1 alleles shows the presence of 2 clades that are primarily associated with <i>A</i>. <i>semotus</i> mtDNA haplotypes, and are unique to the Hawaiian Islands. There is evidence for low levels of hybridization between <i>A</i>. <i>semotus</i> and <i>A</i>. <i>cinereus</i> on the Hawaiian Islands, but it is not extensive (<15% of individuals are of hybrid origin), and clearly each species is able to maintain its own genetic distinctiveness. Both mtDNA and nuclear DNA sequences show deep divergence between the 3 groups (genera) of lasiurine bats that correspond to the previously recognized morphological differences between them. We show that the Tribe Lasiurini contains the genera <i>Aeorestes</i> (hoary bats), <i>Lasiurus</i> (red bats), and <i>Dasypterus</i> (yellow bats).</p></div

Haplotype networks based on mtDNA COI sequences.

<p>A) Network of haplotypes from North American and Hawaiian samples, colored to show the corresponding CMA1 alleles of individuals with the particular COI haplotype group (i.e. if the CMA1 alleles grouped with <i>A</i>. <i>semotus</i>, then it is colored light gray. If there was one allele each from <i>A</i>. <i>semotus</i> and <i>A</i>. <i>cinereus</i>, it is colored dark gray for “mixed.”). Only samples that were sequenced for both CMA1 and COI were included. B) Network of haplotypes from all North American and Hawaiian samples, colored by the geographic origin of the samples. Any discrepancies between parts A and B are due to the elimination of some samples in part A that were not sequenced for CMA1. Black dots represent inferred (unsampled) haplotypes.</p

Divergence date estimates.

<p>The phylogeny is based on a Bayesian divergence time analysis from one individual of each species for 5 genes (COI, Cytb, ND1, ND2, and CMA1). Bars at nodes represent error estimates. All nodes were supported with a Bayesian posterior probability of 1.0. NA = North America; SA = South America.</p

Percent sequence divergence values for Cytb.

<p>Percent sequence divergence values for Cytb.</p

Allele-specific primers used in nuclear gene sequencing.

<p>Allele-specific primers used in nuclear gene sequencing.</p

List of samples used and their associated GenBank accession numbers.

<p>List of samples used and their associated GenBank accession numbers.</p

Extended Bayesian skyline plots based on combined CMA1 and COI sequences.

<p>A) Skyline plot for <i>A</i>. <i>semotus</i> only. B) Skyline plot for <i>A</i>. <i>cinereus</i> from the Hawaiian Islands only. Species classifications are based on mtDNA haplotype.</p