Modern Insect Extinctions, the Neglected Majority

Abstract:  Most extinctions estimated to have occurred in the historical past, or predicted to occur in the future, are of insects. Despite this, the study of insect extinctions has been neglected. Only 70 modern insect extinctions have been documented, although thousands are estimated to have occurred. By focusing on some of the 70 documented extinctions as case studies, I considered ways in which insect extinctions may differ from those of other taxa. These case studies suggested that two types of extinction might be common for insects but rare for other taxa: extinction of narrow habitat specialists and coextinctions of affiliates with the extinctions of their hosts. Importantly, both of these forms of extinction are often ignored by conservation programs focused on vertebrates and plants. Anecdotal evidence and recent simulations suggest that many insect extinctions may have already occurred because of loss of narrow habitat specialists from restricted habitats and the loss of hosts. If we are serious about insect conservation, we need to spend more time and money documenting such extinctions. To neglect such extinctions is to ignore the majority of species that are or were in need of conservation.     

Environmental Synergisms and Extinctions of Tropical Species

Abstract: Environmental synergisms may pose the greatest threat to tropical biodiversity. Using recently updated data sets from the International Union for Conservation of Nature (IUCN) Red List, we evaluated the incidence of perceived threats to all known mammal, bird, and amphibian species in tropical forests. Vulnerable, endangered, and extinct species were collectively far more likely to be imperiled by combinations of threats than expected by chance. Among 45 possible pairwise combinations of 10 different threats, 69%, 93%, and 71% were significantly more frequent than expected for threatened mammals, birds, and amphibians, respectively, even with a stringent Bonferroni‐corrected probability value (p= 0.003). Based on this analysis, we identified five key environmental synergisms in the tropics and speculate on the existence of others. The most important involve interactions between habitat loss or alteration (from agriculture, urban sprawl, infrastructure, or logging) and other anthropogenic disturbances such as hunting, fire, exotic‐species invasions, or pollution. Climatic change and emerging pathogens also can interact with other threats. We assert that environmental synergisms are more likely the norm than the exception for threatened species and ecosystems, can vary markedly in nature among geographic regions and taxa, and may be exceedingly difficult to predict in terms of their ultimate impacts. The perils posed by environmental synergisms highlight the need for a precautionary approach to tropical biodiversity conservation.     

The Role of Behavior in Recent Avian Extinctions and Endangerments

Abstract: Understanding patterns of differential extinction and predicting the relative risks of extinction among extant species are among the most important problems in conservation biology. Although recent studies reveal that behavior can be a critical component in many species' extinctions or endangerments, current approaches to the problem of predicting extinction patterns largely ignore behavior. I reviewed how behavior can affect population persistence and then used recent avian extinctions and endangerments to illustrate behaviors relevant to extinction risk. Behaviors that affect population persistence can be grouped as aggregation, interspecific responses, dispersal, habitat selection, intraspecific behavior, and maladaptive behavior. Behavior that can affect extinction risk is not limited to birds; for example, in many taxonomic groups (vertebrate and invertebrate) there is evidence of socially facilitated reproduction in colonial species, Allee effects on reproductive success and survival, behavioral regulation of population size, and conspecific attraction to breeding sites. Incorporating specific behaviors into models predicting extinction probabilities and patterns should improve their predictions.     

Missing Mammals on Great Basin Mountains: Holocene Extinctions and Inadequate Knowledge

The discontinuous distribution of boreal mammals across Great Basin mountains has provided a significant body of data for the analysis of biogeographic patterns in isolated populations of small mammals. Such use assumes that species unreported from particular ranges do not, in fact, occur there. Data from the Roberts and Diamond mountains (central Nevada) demonstrate that this assumption is incorrect. The new distributional records from these ranges further decrease the slope of the log species—log area relationship for Great Basin boreal mammals, but increase the nestedness of the montane faunas involved. These data underscore the need for more-thorough assessments of the mammalian faunas of Great Basin mountains, but they also suggest that extinction of boreal mammals on these mountains is even more predictable than has appeared in the past.     

Using Montane Mammals to Model Extinctions Due to Global Change

We use data on the species-area relationship and the nested subset structure of the boreal mammal faunas inhabiting isolated mountaintops in the Great Basin to develop a simple quantitative model that predicts the number and identity of species that would go extinct under an assumed scenario of changing climate and vegetation. Global warming of 3°C is predicted to cause the loss of 9–62% of the species inhabiting each mountain range and the extinction of three of fourteen species throughout the region. These results suggest (1) that it is possible to make highly plausible predictions about the susceptibility of species to extinction without detailed information about their population biology, and (2) that global and regional environmental changes seriously threaten the survival of species that are restricted in distribution to both natural "habitat islands" and biological reserves.     

Climate Change, Elevational Range Shifts, and Bird Extinctions

Abstract:  Limitations imposed on species ranges by the climatic, ecological, and physiological effects of elevation are important determinants of extinction risk. We modeled the effects of elevational limits on the extinction risk of landbirds, 87% of all bird species. Elevational limitation of range size explained 97% of the variation in the probability of being in a World Conservation Union category of extinction risk. Our model that combined elevational ranges, four Millennium Assessment habitat-loss scenarios, and an intermediate estimate of surface warming of 2.8° C, projected a best guess of 400–550 landbird extinctions, and that approximately 2150 additional species would be at risk of extinction by 2100. For Western Hemisphere landbirds, intermediate extinction estimates based on climate-induced changes in actual distributions ranged from 1.3% (1.1° C warming) to 30.0% (6.4° C warming) of these species. Worldwide, every degree of warming projected a nonlinear increase in bird extinctions of about 100–500 species. Only 21% of the species predicted to become extinct in our scenarios are currently considered threatened with extinction. Different habitat-loss and surface-warming scenarios predicted substantially different futures for landbird species. To improve the precision of climate-induced extinction estimates, there is an urgent need for high-resolution measurements of shifts in the elevational ranges of species. Given the accelerating influence of climate change on species distributions and conservation, using elevational limits in a tested, standardized, and robust manner can improve conservation assessments of terrestrial species and will help identify species that are most vulnerable to global climate change. Our climate-induced extinction estimates are broadly similar to those of bird species at risk from other factors, but these estimates largely involve different sets of species.     

Forest Fragmentation and Bird Extinctions: San Antonio Eighty Years Later

We report on the extent of bird extinctions at San Antonio, a fragmented cloud forest site in the western Andes of Colombia, for which surveys dating back to 1911 and 1959 an available. In 1911, 128 forest bird species were present in San Antonio. Twenty-four species had disappeared by 1959, and since then 16 more species have gone locally extinct, for a total of 40 species or 31% of the original avifauna. We analyzed patterns of extinction in relation to geographic distribution and foraging guilds. We found that in this montane assemblage, being at the limits of the altitudinal distribution was the main correlate of extinction; 37% of the extinct species were at the upper limit of their altiudinal distribution. We also found that the most vulnerable guilds were the understory insectivores and the large canopy frugivores. Our study illustrates the extent of bird extinctions that are currently undocumented in the highly fragmented forests of the northern Andes, where the absence of baseline information on the fauna of unaltered forests is a limiting factor for the development of conservation and management plans. We stress the need to establish data bases and long-term monitoring projects for the Andean fauna.     

Evolutionary Consequences of Extinctions in Populations of a Hawaiian Honeycreeper

We report on the evolutionary change in bill size of a species of Hawaiian honeycreeper resulting from an apparent dietary shift caused by dramatic declines and extinctions of lobelioids, a historically favored nectar source. Although it now feeds mainly on the flowers of the ohia tree ( Metrosideros polymorpha ), early Hawaiian avifaunal accounts report that the i'iwi ( Vestiaria coccinea ), which has a long decurved bill, fed primarily on the flowers of Hawaiian Lobelioideae, which typically have long decurved corollas. A coevolutionary association of i'iwi bill and flower morphology has often been asserted. We test the hypothesis that the shift in the i'iwi's diet from the long corolla lobelioid flowers to ohia flowers, which lack corollas, resulted in directional selection for shorter bills. We evaluate this hypothesis by comparing the morphological characters of museum specimens from the island of Hawaii collected before 1902 with recent specimens from the Hakalau National Wildlife Refuge, Hawaii. We examine evidence of change in morphological characters using multivariate analysis and a nonparametric cubic spline technique. Results from all analyses are congruent: bill length is shorter in recent specimens.     

Consistent Ecological Selectivity through Time in Pacific Island Avian Extinctions

Abstract: Understanding the ecological mechanisms that lead to extinction is a central goal of conservation. Can understanding ancient avian extinctions help to predict extinction risk in modern birds? I used classification trees trained on both paleoecological and historical data from islands across the Pacific to determine the ecological traits associated with extinction risk. Intrinsic traits, including endemism, large body size, and certain feeding guilds, were tightly linked with avian extinction over the past 3500 years. Species ecology and phylogeny were better predictors of extinction risk through time than extrinsic or abiotic factors. Although human impacts on birds and their habitats have changed over time, modern endangered birds share many of the same ecological characteristics as victims of previous extinction waves. My use of detailed predictions of extinction risk to identify species potentially in need of conservation attention demonstrates the utility of paleoecological knowledge for modern conservation biology.     

Two Hundred Years of Local Avian Extinctions in Eastern Amazonia

Local, regional, and global extinctions caused by habitat loss, degradation, and fragmentation have been widely reported for the tropics. The patterns and drivers of this loss of species are now increasingly well known in Amazonia, but there remains a significant gap in understanding of long‐term trends in species persistence and extinction in anthropogenic landscapes. Such a historical perspective is critical for understanding the status and trends of extant biodiversity as well as for identifying priorities to halt further losses. Using extensive historical data sets of specimen records and results of contemporary surveys, we searched for evidence of local extinctions of a terra firma rainforest avifauna over 200 years in a 2500 km² eastern Amazonian region around the Brazilian city of Belém. This region has the longest history of ornithological fieldwork in the entire Amazon basin and lies in the highly threatened Belém Centre of Endemism. We also compared our historically inferred extinction events with extensive data on species occurrences in a sample of catchments in a nearby municipality (Paragominas) that encompass a gradient of past forest loss. We found evidence for the possible extinction of 47 species (14% of the regional species pool) that were unreported from 1980 to 2013 (80% last recorded between 1900 and 1980). Seventeen species appear on the International Union for Conservation of Nature Red List, and many of these are large‐bodied. The species lost from the region immediately around Belém are similar to those which are currently restricted to well‐forested catchments in Paragominas. Although we anticipate the future rediscovery or recolonization of some species inferred to be extinct by our calculations, we also expect that there are likely to be additional local extinctions, not reported here, given the ongoing loss and degradation of remaining areas of native vegetation across eastern Amazonia. Doscientos Años de Extinciones Locales de Aves en la Amazonia Oriental