Extinction Debt in Source-Sink Metacommunities

Abstract

In an increasingly modified world, understanding and predicting the consequences of landscape alteration on biodiversity is a challenge for ecologists. To this end, metacommunity theory has developed to better understand the complexity of local and regional interactions that occur across larger landscapes. While metacommunity ecology has now provided several alternative models of species coexistence at different spatial scales, predictions regarding the consequences of landscape alteration have been done exclusively for the competition-colonization trade off model (CC). In this paper we investigate the effects of landscape perturbation on source-sink metacommunities. We show that habitat destruction perturbs the equilibria among species competitive effects within the metacommunity, driving both direct extinctions and an indirect extinction debt. As in CC models, we found a time lag for extinction following habitat destruction that varied in length depending upon the relative importance of direct and indirect effects. However, in contrast to CC models, we found that the less competitive species are more affected by habitat destruction. The best competitors can sometimes even be positively affected by habitat destruction, which corresponds well with the results of field studies. Our results are complementary to those results found in CC models of metacommunity dynamics. From a conservation perspective, our results illustrate that landscape alteration jeopardizes species coexistence in patchy landscapes through complex indirect effects and delayed extinctions patterns.

Relaxation Time and the Problem of the Pleistocene

“…In all cases, relaxation time is approached asymptotically with much of the diversity change experience in the early part of the relaxation period. These relaxation times are similar to or longer than estimates based on modern terrestrial faunas [26,36,37] and other models [27,38,39], suggesting that relaxation times are unlikely to be substantially longer than simulated here.…”

Drought-driven change in wildlife distribution and numbers: a case study of koalas in south west Queensland

“…There are already delays between habitat clearance and loss of species, leading to an extinction debt (Tilman et al 1994;Mouquet et al 2011), and the extinction debt may contribute to the finding of Anderson et al (2009) that changes in trailing-edge populations happen more slowly than those in leading-edge expansion. The interaction of habitat loss, fragmentation, and climate extremes will increase pressure on some populations and species, particularly in isolated trailing-edge populations where dispersal ability is limited (Travis 2003;Thomas et al 2004).…”

“…Habitat fragmentation has a range of effects on forest-dependent mammals, including: decreases in habitat amount and quality; lower breeding and dispersal success; and increased risk of mortality due to predation or collisions with motor vehicles (Andrén 1994;Cogger et al 2003;Fahrig 2003;McAlpine et al 2006a). Changes in distribution and numbers may lag behind habitat clearance, resulting in an extinction debt (Tilman et al 1994;Mouquet et al 2011). The 2006 State of the Environment report for Australia identified that loss of native vegetation continues to be one of the greatest threats to biodiversity (Beeton et al 2006).…”

Adaptation to fragmentation: evolutionary dynamics driven by human influences

“…decreased dispersal: increased risk of dispersal due to increased extent or harshness of the matrix between patches fast evolution of reduced dispersal in Asteraceae species on islands after colonization [1]; evolution of reduced dispersal in spiders in salt marshes of different sizes in European estuaries [3]; evolution of flightlessness in insects (woodlands, deserts, islands, etc.) [5] reduced dispersal in Crepis sancta in less than 12 generations after colonization of soil patches in urban sidewalks [2]; reduction of dispersal motivation in spiders from dune grassland fragments [4]; reduced migratory behaviour in Oncorhynchus mykiss consecutive to river isolation [6] increased dispersal: increased colonization advantage of dispersal high dispersal in Western bluebirds colonizing disturbed areas and are replaced by phylopatric bluebird along the succession (over a 20 -30 years cycle) [7]; sorting of dispersive genotypes in Aland archipelago metapopulations of glanville fritillary butterfly [9] evolution of flight-related morphology (with putative effect on dispersal) in a butterfly from recently fragmented grassland fragments [8]; evolution of mobility related morphology (with putative effect on dispersal) in a grasshopper [10]; selection for increased perceptual range in fragmented landscapes to reduce dispersal costs [11] demographic: Allee effects small populations unable to attract pollinators variable herkogamy and autonomous selfing in small and large populations of Gentianella germanica [12] physical: edge effects increased niche breath none none community: altered biotic interactions loss of antagonistic interactions and trait evolution evolution of reduced mobility by relaxed selection from predators on islands [13] reduced defense in Ambrosia artemisiifolia in free enemy invasive areas [13]; rapid decrease in alewife gill-raker spacing caused by predation [14] loss of mutualistic interactions and trait evolution absence of specialist bee pollinators leading to reduced herkogamy and higher autofertility in Clarkia [15] evolution of selfing in Centaurium erythraea in the absence of pollinators [16]; rapid evolutionary changes in seed size consecutive to bird disperser extinction [17] altered multitrophic interactions and coevolutionary dynamics morphological evolution in naturally clustered plants interacting with both herbivores and pollinators [18]; phytoplankton composition modifies predator-driven life-history evolution in Daphnia [19]; the mosaic of coevolution of plant -pollinator-herbivore interactions [20] (Continu...…”

“…The effects of fragmentation have historically been studied using the framework of island biogeography [4]. However, more recent work has broadened this scope to include population genetics [5], metapopulation [6] and metacommunity theory [7].…”