Passive sampling effects and landscape location alter associations between species traits and response to fragmentation

Abstract

As tropical reserves become smaller and more isolated, the ability of species to utilize fragmented landscapes will be a key determinant of species survival. Although several ecological and life history traits commonly are associated with vulnerability to fragmentation, the combination of traits that are most highly influential and the effectiveness of those traits in predicting vulnerability across distinct landscapes, remains poorly understood. We studied use of forest fragments by 25 mid- and large-sized neotropical mammals in Guatemala to determine how seven species traits influence vulnerability to fragmentation. We measured vulnerability in two ways: one measure that did not remove passive sampling effects (proportion of fragments occupied), and one that did (difference in occupancy rates within continuous and fragmented sites). We also examined the influence of species traits on patch occupancy rates of the same set of mammals on two landscapes in Mexico. When not accounting for passive sampling effects, body size, home range size, and vulnerability to hunting influenced how species responded to fragmentation. However, after controlling for passive sampling effects, only vulnerability to hunting strongly influenced sensitivity to fragmentation. Species that were heavily hunted were much less common in forest patches than in continuous forest sites of the same sampling size. The cross-landscape comparison revealed both similarities and differences in the species traits that influenced patch occupancy patterns on each landscape. Given the ubiquity of hunting in tropical environments, our findings indicate that management efforts in fragmented landscapes that do not account for hunting pressure may be ineffective in conserving heavily hunted tropical species. Our study also indicates that species traits may be useful in predicting relative patch occupancy rates and/or vulnerability to fragmentation across distinct landscapes, but that caution must be used as certain traits can become more or less influential on different landscapes, even when considering the same set of species.

Species traits explaining sensitivity of snakes to human land use estimated from citizen science data

“…For example, imperilment has been shown almost universally to increase with body size for most species (e.g., Purvis et al, 2000;Cardillo et al, 2008), including reptiles (Tingley et al, 2013;Böhm et al, 2016). Nevertheless, a direct link between body size in vertebrates and sensitivity to habitat loss or human land use has proven elusive across many taxa (Swihart et al, 2003;Meyer et al, 2008;Thornton et al, 2011;Vetter et al, 2011;Quesnelle et al, 2014), and our results agree with these earlier findings. Body size may not generally correlate well with sensitivity to habitat loss because it is linked to many other life-history attributes that more directly predispose species to imperilment risks, including trophic level and fecundity, among others (Henle et al, 2004).…”

Ecological correlates of vulnerability to fragmentation in forest birds on inundated subtropical land-bridge islands

“…Soulé et al, 1988;Swihart et al, 2003;Viveiros de Castro and Fernandez, 2004;Meyer et al, 2008;). Following Thornton et al (2011a), we used occupancy modeling as implemented in the program PRESENCE (Hines, 2014) to compute the proportion of islands occupied by each species that controlled for imperfect detection as the measure of vulnerability to fragmentation. The results of the proportion of islands occupied corrected for detectability were then compared with that of naïve proportion of islands occupied by bird species to test our first hypothesis that imperfect detection would influence the identification of the relationships between species traits and fragmentation vulnerability (MacKenzie et al, 2002).…”

“…We made the following three hypotheses. First, we hypothesized that imperfect detection would influence the identification of the relationships between species traits and fragmentation vulnerability (MacKenzie et al, 2002;Thornton et al, 2011a). Second, we hypothesized that we would find nonadditive relationships between at least some of the eight traits, given the prevalence of the idea of synergistic interactions in the literature (Lawton, 1994;Davies et al, 2004).…”

Functional Diversity Metrics: How They Are Affected by Landscape Change and How They Represent Ecosystem Functioning in the Tropics

“…There may also be geographic differences, with abiotic and biotic factors unique to a particular site or region, exerting a strong influence on the nature of functional changes. The role of temporal and site-specific differences is starting to be recognised when comparing sensitivity (or response) traits to landscape change [54][55][56], and the situation may be similar for functional traits, making generalisation difficult.…”