To assess the historical biogeography of freshwater topminnows in the genus Poeciliopsis, we examined sequence variation in two mitochondrial genes, cytochrome b (1140 bp) and NADH subunit 2 (1047 ...bp). This widespread fish genus is distributed from Arizona to western Colombia, and nearly half of its 21 named species have distributions that border on the geologically active Trans‐Mexican Volcanic Belt (TMVB), a region that defines the uplifted plateau (Mesa Central) of Mexico. We used the parametric bootstrap method to test the hypothesis that a single vicariant event associated with the TMVB was responsible for divergence of taxa found to the north and south of this boundary. Because the single‐event hypothesis was rejected as highly unlikely, we hypothesize that at least two geological events were responsible for divergence of these species. The first (8–16 million years ago) separated ancestral populations that were distributed across the present TMVB region. A second event (2.8–6.4 million years ago) was associated with northward dispersal and subsequent vicariance of two independent southern lineages across the TMVB. The geological history of this tectonically and volcanically active region is discussed and systematic implications for the genus are outlined.
Most bees rely on flowering plants and hence are diurnal foragers. From this ancestral state, dim-light foraging in bees requires significant adaptations to a new photic environment. We used DNA ...sequences to evaluate the phylogenetic history of the most diverse clade of Apoidea that is adapted to dim-light environments (Augochlorini: Megalopta, Megaloptidia and Megommation). The most speciose lineage, Megalopta, is distal to the remaining dim-light genera, and its closest diurnal relative (Xenochlora) is recovered as a lineage that has secondarily reverted to diurnal foraging. Tests for adaptive protein evolution indicate that long-wavelength opsin shows strong evidence of stabilizing selection, with no more than five codons (2%) under positive selection, depending on analytical procedure. In the branch leading to Megalopta, the amino acid of the single positively selected codon is conserved among ancestral Halictidae examined, and is homologous to codons known to influence molecular structure at the chromophore-binding pocket. Theoretically, such mutations can shift photopigment λmax sensitivity and enable visual transduction in alternate photic environments. Results are discussed in light of the available evidence on photopigment structure, morphological specialization and biogeographic distributions over geological time.
Abstract
Squamates include all lizards and snakes, and display some of the most diverse and extreme morphological adaptations among vertebrates. However, compared with birds and mammals, relatively ...few resources exist for comparative genomic analyses of squamates, hampering efforts to understand the molecular bases of phenotypic diversification in such a speciose clade. In particular, the ∼400 species of anole lizard represent an extensive squamate radiation. Here, we sequence and assemble the draft genomes of three anole species—Anolis frenatus, Anolis auratus, and Anolis apletophallus—for comparison with the available reference genome of Anolis carolinensis. Comparative analyses reveal a rapid background rate of molecular evolution consistent with a model of punctuated equilibrium, and strong purifying selection on functional genomic elements in anoles. We find evidence for accelerated evolution in genes involved in behavior, sensory perception, and reproduction, as well as in genes regulating limb bud development and hindlimb specification. Morphometric analyses of anole fore and hindlimbs corroborated these findings. We detect signatures of positive selection across several genes related to the development and regulation of the forebrain, hormones, and the iguanian lizard dewlap, suggesting molecular changes underlying behavioral adaptations known to reinforce species boundaries were a key component in the diversification of anole lizards.
We report
Anopheles darlingi
in Darien Province in eastern Panama. Polymerase chain reaction–restriction fragment length polymorphism profiles of the single copy nuclear
white
gene and sequence ...comparisons confirmed the presence of 66 specimens of the northern lineage of
An. darlingi
. The parsimony network depicted 5
CO1
haplotypes in 40 specimens of
An. darlingi
, which connected through 7–8 mutational steps with sequences from Central and South America. Furthermore, the presence of haplotypes in Biroquera, Darien Province identical to those previously published from northern Colombia suggests that Panamanian samples originated in Colombia. Results of neutrality tests (
R
2
and Fu’s
F
S
) were not significant and the mismatch distribution was multimodal and did not fit the model of sudden population growth. These findings may indicate a long and stable presence of
An. darlingi
in eastern Panama.
The present study shows new evidence of morphological traits that supports the hypothesis of diversification between two genetic variants of Pelliciera rhizophorae (Tetrameristaceae), the most ...ancient species in the Neotropical mangrove ecosystem. Previous studies using molecular markers identified two variants of this species. Our new study, using pollen grain morphology, revealed differences in pollen sculpture between the two variants; that is, in Variant A the exine is characterised as perforate—verrucose, while in Variant B, it is punctuate. Pollen size in Variant A is larger than in Variant B, whereas the exine is thicker in Variant B than in Variant A. The differences in pollen morphology between the two variants represent new evidence suggesting that a diversification process might be occurring within P. rhizophorae, possibly due to adaptive processes in response to environmental conditions or pollination vectors.
The Central American Isthmus (CAI) is an important geographic barrier in the Neotropics. Its role in the diversification of marine and coastal species has been detected in fishes, turtles, sea ...urchins, and mangroves. We evaluated the CAI’s influence on the diversification of the most ancient neotropical mangrove species
Pelliciera rhizophorae
across populations from the Caribbean and Pacific coasts, based on the analysis of ten nuclear microsatellite loci and two noncoding chloroplast DNA regions. The two molecular markers showed concordant patterns of diversification in this mangrove species. Contrary to our expectations, this study did not reveal significant genetic structure among populations separated by the CAI. Two major genetic variants (cluster I and cluster II) were found on both coasts, but the two were not found intermixed in the same population. Within each coastal region, breaking of gene flow among populations was found at two points in the Pacific Basin and one point in the Caribbean Basin, separating the Colombian and Panamanian populations. Our study revealed a transisthmian connection among populations of
P. rhizophorae
. This result, together with the reduced genetic diversity in the Caribbean reported in our previous study, suggests the recent origin of these populations, probably due to reintroduction of
P. rhizophorae
from the Pacific coast. Taking into account that these introductions are random events, this study raises a new question: Why are genetic variants not intermixed within the Caribbean populations? Our hypotheses suggest the influence of environmental factors and/or anthropogenic impact on the establishment of these Caribbean patches.
The pathogenic chytrid fungus,
Batrachochytrium dendrobatidis
, has been implicated as the main driver of many enigmatic amphibian declines in neotropical sites at high elevation.
Batrachochytrium ...dendrobatidis
is thought to be a waterborne pathogen limited by temperature, and the extent to which it persists and causes disease in amphibians at lower elevations in the neotropics is not known. It also is unclear by what mechanism(s)
B. dendrobatidis
has emerged as a pathogenic organism. To test whether
B. dendrobatidis
is limited by elevation in Panamá, we sought to determine the prevalence and intensity of
B. dendrobatidis
in relation to anuran abundance and diversity using quantitative PCR (qPCR) analyses. Sites were situated at varying elevations, from 45 to 1215 m, and were at varying stages of epizootic amphibian decline, including pre-epizootic, mid-epizootic, 2 years post-epizootic, and 10 years post-epizootic.
Batrachochytrium dendrobatidis
was found in all sites regardless of elevation or stage of epizootic decline. Levels of prevalence and infection intensity were comparable across all sites except at the mid-epizootic site, where both prevalence and intensity were significantly higher than at other sites. Symptoms of chytridiomycosis and corresponding declines in amphibian populations were variably seen at all elevations along a post-epizootic gradient. Because it is inherently difficult to prove a negative proposition, it can neither be proven that
B. dendrobatidis
is truly not present where it is not detected nor proven that it is only recently arrived where it is detected. Thus, there will always be doubts about whether
B. dendrobatidis
is enzootic or invasive. In any case, our results, coupled with current knowledge, suggest most clearly that the disease, chytridiomycosis, may be novel and invasive, and that the pathogen,
B. dendrobatidis
either is, or is becoming, globally ubiquitous.
Tapirs (Tapirus sp.) have been studied extensively in the wild, yet little is known about their fundamental reproductive biology, information that is critical to establishing self‐sustaining ...populations in captivity as a hedge against extinction. This paper reviews information on the reproductive biology of the 4 species of tapirs: Baird's (Tapirus bairdii), lowland (T terrestris), mountain (T pinchaque) and Malayan (T indicus). Both sexes reach puberty between 14 and 48 months of age. Behaviorally, tapirs display few overt signs of estrus, and external signs of pregnancy are not evident until approximately 2 months before parturition. Immunoassay techniques to measure reproductive hormones in blood and urine have been validated for tapirs, which allow monitoring of ovarian cycle activity and pregnancy. Data indicate that females are polyestrous, with an estrous cycle length of approximately 30 days. The exception is the Malayan tapir, which exhibits 2 types of cycles: short (approximately 1 month) and long (approximately 2 months). Gestation length is approximately 13 months and females can conceive at the first post‐partum cycle within 1 month after birth. Good quality ejaculates have been obtained via electroejaculation in the Baird's and Malayan tapir and the sperm from Baird's tapir cryopreserved using standard cryodiluents, although more work is needed to optimize these protocols. Given that all 4 species of tapir most likely will continue to be maintained in captivity, effective genetic management is vital for long‐term survival. Optimization of assisted reproductive technologies, including sperm cryopreservation and artificial insemination, could benefit the genetic management of tapirs.
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