Requiem for the Tricolored Blackbird in Mexico?

We summarize existing literature and document a recent steep population decline and range contraction in the Tricolored Blackbird (Agelaius tricolor) at the southern end of its range, in Baja California, the only state of Mexico in which the species occurs. From >1000 nesting birds using at least 14 sites south to 30° N around the turn of the 21st century, the population declined and contracted northward and upward in elevation to a single colony of ~150 nesting birds near the international border in 2019. Chronic drought, rising temperatures, and habitat losses due primarily to intensification of agriculture in Mexico are largely responsible for the decline, as in the core of the species’ range in California. Because of the reduction of breeding and foraging habitat, we fear the imminent extirpation of the species in Mexico.

Combined impacts of climate and land use change and the future of Neotropical bat biodiversity

Forecasting the effects of global change on biodiversity is necessary to anticipate the threats operating at different scales in space and time. Climate change may create unsuitable environmental conditions, forcing species to move to persist. However, land-use changes create barriers that limit the access of some species to future available habitats. Here, we project the impacts of climate and land-use change on 228 Neotropical bat species by forecasting changes in environmental suitability, while accounting for the effect of habitat type specialization and simulating dispersal across suitable patches. We also identify the most vulnerable ecoregions and those that may offer future stable refugia. We further investigate potential functional changes by analysing the response of different trophic guilds. We found that the range contraction of habitat specialists, especially frugivores, was more frequent and stronger under all simulated scenarios. Projected changes differ markedly across ecoregions. While the Amazon region is likely to undergo high turnover rates in bat composition, the Andean grassland, Cerrado and Chaco might experience the greatest losses. The expansion of habitat generalists, which forage in open areas and commonly establish large colonies in manmade structures, coupled with the range contraction of habitat specialists is projected to homogenize bat communities across the Neotropics. Overall, dispersal will likely be the key for the future of Neotropical bat diversity. Therefore, safeguarding the refugia highlighted here, by expanding and connecting the existing network of protected areas, for example, may allow species to move in response to global change.

Phylogenomic insights into the divergent history and hybridization within the East Asian endemic Abelia (Caprifoliaceae)

Background and Aims Abelia (Caprifoliaceae) is a small genus with five species (including one artificial hybrid). The genus has a disjunct distribution across mainland China, Taiwan and the Ryukyu Islands, providing a model system to explore species dispersal mechanisms of the East Asian flora. However, the current phylogenetic relationships within Abelia remain controversial. Methods In this study, we reconstructed the phylogenetic relationships within Abelia using nuclear loci generated by target enrichment and the cpDNA from genome skimming. Key Results: We found large cytonuclear discordance across the genus. Based on the nuclear and chloroplast phylogenies we proposed to merge A. schumannii into A. macrotera, and A. macrotera var. mairei into A. uniflora. Divergence time estimation, ancestral area reconstruction, and ecological niche modelling (ENM) were used to examine the biogeographic history of Abelia. Our results showed that Abelia originated in Southwest China, and diversification began in the Early Eocene, followed by A. chinensis var. ionandra colonizing Taiwan in the Middle Miocene. The ENM results suggested an expansion of climatically suitable areas during the Last Glacial Maximum and range contraction during the Last Interglacial. Disjunction between the Himalaya-Hengduan Mountain region (HHM) and Taiwan is most likely the consequence of topographic isolation and postglacial contraction. Conclusions Overall, our results supports that postglacial range contraction together with topographic heterogeneity resulted in the Taiwan and China mainland disjunction. Furthermore, when we using genome data to reconstruct the phylogeny of related species, branch evolution and network evolution should be considered, as well as gene flow in historical periods. This research provide new insights for the speciation process and taxonomy of Abelia.

Overfishing and habitat loss drive range contraction of iconic marine fishes to near extinction

Extinctions on land are often inferred from sparse sightings over time, but this technique is ill-suited for wide-ranging species. We develop a space-for-time approach to track the spatial contraction and drivers of decline of sawfishes. These iconic and endangered shark-like rays were once found in warm, coastal waters of 90 nations and are now presumed extinct in more than half (n = 46). Using dynamic geography theory, we predict that sawfishes are gone from at least nine additional nations. Overfishing and habitat loss have reduced spatial occupancy, leading to local extinctions in 55 of the 90 nations, which equates to 58.7% of their historical distribution. Retention bans and habitat protections are urgently necessary to secure a future for sawfishes and similar species.

Paths to annihilation: Genetic and demographic consequences of range contraction patterns

ABSTRACTSpecies range contractions are important contributors to biological annihilation, yet typically do not receive the same attention as extinctions. Range contractions can lead to marked impacts on populations but are often only characterized by measurements of reduced extent. For effective conservation efforts, it is critical to recognize that not all range contractions are the same. We propose four distinct patterns of range contraction: shrinkage, amputation, hollow, and fragmentation. We tested their impact on populations of a generic generalist species using forward-time simulations. Results showed that all four patterns differentially reduced population abundance (declines of 60-80%) and significantly increased average relatedness, with differing patterns in nucleotide diversity (π) declines relative to the contraction pattern. The fragmentation pattern resulted in the strongest effects on post-contraction genetic diversity and structure. Defining and quantifying range contraction patterns and their consequences for the planet’s biodiversity provides necessary information to combat biological annihilation in the Anthropocene.