2018 Annual Report

In 2018, the Museum of Southwestern Biology (MSB) has continued to improve its profile and impacts, both on the University of New Mexico campus and in the international scientific community. Its collections serve as scientific infrastructure that enhances research, teaching, community service, and public outreach. The MSB is part of the UNM Department of Biology, and the missions of the MSB and the Department are synergistic. MSB houses extensive and rapidly growing collections representing biodiversity of world, primarily from the last halfcentury. MSB has outstanding collections from New Mexico and western North America, but it also has substantial holdings from five other continents around the world. MSB consists of eight divisions, and one special program (the Natural Heritage Program New Mexico). MSB also manages the large federal collection of the US Geological Survey collection, second only the Smithsonian Institution in size among federal collections. The collections enrich education by allowing for scientists, educators, public health professionals, and natural resource managers to investigate climate change, environmental quality, emerging diseases, invasive species, ecology, genomics, and evolution. The databases associated with the MSB\u27s eight collections constitute a significant, accessible informatics resource that grows in value each time scientific research is done using the collections. In these ways, MSB contributes to understanding life on earth, its origins, diversity, function, and relationships with human society and public health. MSB annual reports are archived and accessible via UNM\u27s internet repository: (http://repository.unm.edu/handle/1928/24433).https://digitalrepository.unm.edu/msb_annual_reports/1012/thumbnail.jp

Rates of molecular evolution and their application to neotropical avian biogeography

The tempo of evolution and the causes of rate variation among lineages are central foci of evolutionary biology. I evaluated two hypothesized sources of variation in molecular evolutionary rate, and I applied a variable molecular clock to estimate the timescale of diversification in three families of Neotropical birds. First, I examined the phylogenetic evidence for molecular punctuated equilibrium, the hypothesis that speciation drives accelerated molecular evolution. Recent findings that rates of DNA evolution and speciation are linked implicate molecular punctuated equilibrium as an important cause of rate variation among lineages. I used phylogenetic simulations to test this reported link, and I found that it was entirely attributable to a methodological artifact. In a review of the topic, I found no unequivocal empirical evidence for molecular punctuated equilibrium and I concluded that its predicted phylogenetic consequences are theoretically implausible. Second, I tested the metabolic rate hypothesis, which holds that mutation rate in mtDNA is correlated with mass-specific metabolic rate. This hypothesis predicts that small-bodied lineages should evolve rapidly. Previous studies verified this prediction, but none utilized adequately large samples of independent contrasts among appropriate taxa. The use of many such contrasts from bird mtDNA sequences conspicuously failed to corroborate the link between metabolic and mtDNA rates. On the contrary, high rates of nonsynonymous substitution were associated with large body mass, implicating population size as a pervasive cause of evolutionary rate variation. Third, I developed molecular phylogenies for puffbirds, jacamars, and motmots to test hypothesized area relationships in the Neotropics. I used penalized likelihood to estimate node times while accommodating significant rate variation under a set of biologically realistic assumptions. Phylogenetic patterns in each family were consistent with expansion following the formation of the Central American Landbridge and subsequent vicariance across the Andes. I applied a calibration based on the final uplift of the Isthmus of Panama, 3.1 Ma. Average estimated rates were close to the commonly cited 2% sequence divergence/Myr. Concordant area relationships were found among co-distributed species complexes; however, the timescale of divergence was variable, suggesting that common dispersal corridors rather than common vicariant events may be driving co-phylogenetic patterns

A review of the status and distribution of the Bornean Bristlehead

We compiled all documented records of Bornean Bristlehead Pityriasis gymnocephata to determine what is known about the life-history and distribution of this enigmatic species. Pityriasis is a relict cracticid, related to the Australian magpies and butcherbirds. It is a highly social species and widespread throughout Borneo in forests below 1000m elevation, but rarely encountered

The status of Abbott's Babbler in Borneo

We reviewed the occurrence of Abbott's Babbler Trichastoma abbotti on Borneo as a first step towards understanding why this species, which is common in most of its range, is so rare on the island. We were able to find only 21 documented Bornean records, most of which derived from areas of scrub habitat at low altitudes, especially near the coast

Natural history and evolution of an elevational generalist, the Cinereous Conebill (Conirostrum cinereum)

Elevational generalism is relatively rare in the tropical Andes Mountains, likely owing to the inherent requirements of enduring a high degree of climatic zonation and coping with hypoxic stress. The Cinereous Conebill (Conirostrum cinereum) appears to be an exception, and inhabits a continuous elevational distribution that spans over 4,500 m. Two subspecies, cinereum and fraseri, are restricted to high elevations and may be isolated, whereas the third and most widespread, littorale, occurs continuously along the western slope of the Andes from 0 to over 4,500 m. First, we aim to characterize the morphology, genetics, and climatic niche of the three subspecies using a comparative biogeographic approach to explore patterns and timing of differentiation and to consider possible mechanisms of diversification. Second, we study whether hemoglobin adaptation plays a role in this elevational generalist’s ability to thrive in high-elevation environments, and whether localized adaptation is possible despite altitudinal migration and gene flow. We used a comparative phylogeographic framework to examine whether lineage divergence within C. cinereum is associated with climatic, geographic, and/or physiological barriers leading to incipient speciation

Gene Turnover in the Avian Globin Gene Families and Evolutionary Changes in Hemoglobin Isoform Expression

The apparent stasis in the evolution of avian chromosomes suggests that birds may have experienced relatively low rates of gene gain and loss in multigene families. To investigate this possibility and to explore the phenotypic consequences of variation in gene copy number, we examined evolutionary changes in the families of genes that encode the α- and β-type subunits of hemoglobin (Hb), the tetrameric α2β2 protein responsible for blood-O2 transport. A comparative genomic analysis of 52 bird species revealed that the size and membership composition of the α- and β-globin gene families have remained remarkably constant during approximately 100 My of avian evolution. Most interspecific variation in gene content is attributable to multiple independent inactivations of the αD-globin gene, which encodes the α-chain subunit of a functionally distinct Hb isoform (HbD) that is expressed in both embryonic and definitive erythrocytes. Due to consistent differences in O2-binding properties between HbD and the major adult-expressed Hb isoform, HbA (which incorporates products of the αA-globin gene), recurrent losses of αD-globin contribute to among-species variation in blood-O2 affinity. Analysis of HbA/HbD expression levels in the red blood cells of 122 bird species revealed high variability among lineages and strong phylogenetic signal. In comparison with the homologous gene clusters in mammals, the low retention rate for lineage-specific gene duplicates in the avian globin gene clusters suggests that the developmental regulation of Hb synthesis in birds may be more highly conserved, with orthologous genes having similar stage-specific expression profiles and similar functional properties in disparate taxa

Predictable convergence in hemoglobin function has unpredictable molecular underpinnings

To investigate the predictability of genetic adaptation, we examined the molecular basis of convergence in hemoglobin function in comparisons involving 56 avian taxa that have contrasting altitudinal range limits. Convergent increases in hemoglobin-oxygen affinity were pervasive among high-altitude taxa, but few such changes were attributable to parallel amino acid substitutions at key residues.Thus, predictable changes in biochemical phenotype do not have a predictable molecular basis. Experiments involving resurrected ancestral proteins revealed that historical substitutions have context-dependent effects, indicating that possible adaptive solutions are contingent on prior history. Mutations that produce an adaptive change in one species may represent precluded possibilities in other species because of differences in genetic background

Predictable convergence in hemoglobin function has unpredictable molecular underpinnings

To investigate the predictability of genetic adaptation, we examined the molecular basis of convergence in hemoglobin function in comparisons involving 56 avian taxa that have contrasting altitudinal range limits. Convergent increases in hemoglobin-oxygen affinity were pervasive among high-altitude taxa, but few such changes were attributable to parallel amino acid substitutions at key residues.Thus, predictable changes in biochemical phenotype do not have a predictable molecular basis. Experiments involving resurrected ancestral proteins revealed that historical substitutions have context-dependent effects, indicating that possible adaptive solutions are contingent on prior history. Mutations that produce an adaptive change in one species may represent precluded possibilities in other species because of differences in genetic background

Molecular Phylogenetics and the Diversification of Hummingbirds

SummaryThe tempo of species diversification in large clades can reveal fundamental evolutionary mechanisms that operate on large temporal and spatial scales [1–4]. Hummingbirds have radiated into a diverse assemblage of specialized nectarivores comprising 338 species, but their evolutionary history has not, until now, been comprehensively explored. We studied hummingbird diversification by estimating a time-calibrated phylogeny for 284 hummingbird species, demonstrating that hummingbirds invaded South America by ∼22 million years ago, and subsequently diversified into nine principal clades (see [5–7]). Using ancestral state reconstruction and diversification analyses, we (1) estimate the age of the crown-group hummingbird assemblage, (2) investigate the timing and patterns of lineage accumulation for hummingbirds overall and regionally, and (3) evaluate the role of Andean uplift in hummingbird speciation. Detailed analyses reveal disparate clade-specific processes that allowed for ongoing species diversification. One factor was significant variation among clades in diversification rates. For example, the nine principal clades of hummingbirds exhibit ∼15-fold variation in net diversification rates, with evidence for accelerated speciation of a clade that includes the Bee, Emerald, and Mountain Gem groups of hummingbirds. A second factor was colonization of key geographic regions, which opened up new ecological niches. For example, some clades diversified in the context of the uplift of the Andes Mountains, whereas others were affected by the formation of the Panamanian land bridge. Finally, although species accumulation is slowing in all groups of hummingbirds, several major clades maintain rapid rates of diversification on par with classical examples of rapid adaptive radiation