Are specialists at risk under environmental change? Neoecological, paleoecological and phylogenetic approaches

Abstract

The question ‘what renders a species extinction prone’ is crucial to biologists. Ecological specialization has been suggested as a major constraint impeding the response of species to environmental changes. Most neoecological studies indicate that specialists suffer declines under recent environmental changes. This was confirmed by many paleoecological studies investigating longer-term survival. However, phylogeneticists, studying the entire histories of lineages, showed that specialists are not trapped in evolutionary dead ends and could even give rise to generalists. Conclusions from these approaches diverge possibly because (i) of approach-specific biases, such as lack of standardization for sampling efforts (neoecology), lack of direct observations of specialization (paleoecology), or binary coding and prevalence of specialists (phylogenetics); (ii) neoecologists focus on habitat specialization; (iii) neoecologists focus on extinction of populations, phylogeneticists on persistence of entire clades through periods of varying extinction and speciation rates; (iv) many phylogeneticists study species in which specialization may result from a lack of constraints. We recommend integrating the three approaches by studying common datasets, and accounting for range-size variation among species, and we suggest novel hypotheses on why certain specialists may not be particularly at risk and consequently why certain generalists deserve no less attention from conservationists than specialists.

Isotopic niches of fin whales from the Mediterranean Sea and the Celtic Sea (North Atlantic)

“…In the event of environmental perturbations, resource specialization can be a disadvantageous evolutionary strategy. Indeed the majority of ecological studies (over both neoand palaeo-timescales) conclude that resource specialization elevates risk of extinction (Colles et al, 2009). Generalists have access to a wider range of resources.…”

The shape of mammalian phylogeny: patterns, processes and scales

“…Unusualness is a statistical concept, of course, and species-rich groups are bound to appear typical, but specialization to a narrow adaptive zone may be the best predictor of species-poverty. We speculate that such specializations may reduce the likelihood of radiation-because the niches are not broad enough to support multiple species in sympatry-but at the same time confer a strong incumbency advantage [50] that reduces the per-species background extinction rate if niches are stable over time [51]. Such a mechanism would lead to species in relictual groups tending to be highly specialized, which is certainly true for some of the species-poor basal clades (e.g.…”

Structure of bird communities in eucalyptus plantations: nestedness as a pattern of species distribution

“…richness, stratification) is an important factor affecting the composition of bird communities (Hobbs et al, 2003;Gabriel, 2009;Filloy et al, 2010;Volpato et al, 2010;Mendonça-Lima, 2012). In silviculture areas, avian communities may consist mainly of habitat generalists, i.e., species that use a relatively wide set of habitat resources (Colles et al, 2009), and species associated with forest edges and open areas.…”