Threshold effect of habitat loss on bat richness in cerrado‐forest landscapes

Abstract

Understanding how animal groups respond to contemporary habitat loss and fragmentation is essential for development of strategies for species conservation. Until now, there has been no consensus about how landscape degradation affects the diversity and distribution of Neotropical bats. Some studies demonstrate population declines and species loss in impacted areas, although the magnitude and generality of these effects on bat community structure are unclear. Empirical fragmentation thresholds predict an accentuated drop in biodiversity, and species richness in particular, when less than 30% of the original amount of habitat in the landscape remains. In this study, we tested whether bat species richness demonstrates this threshold response, based on 48 sites distributed across 12 landscapes with 9-88% remaining forest in Brazilian cerrado-forest formations. We also examined the degree to which abundance was similarly affected within four different feeding guilds. The threshold value for richness, below which bat diversity declines precipitously, was estimated at 47% of remaining forest. To verify if the response of bat abundance to habitat loss differed among feeding guilds, we used a model selection approach based on Akaike's information criterion. Models accounted for the amount of riparian forest, semideciduous forest, cerrado, tree plantations, secondary forest, and the total amount of forest in the landscape. We demonstrate a nonlinear effect of the contribution of tree plantations to frugivores, and a positive effect of the amount of cerrado to nectarivores and animalivores, the groups that responded most to decreases in amount of forest. We suggest that bat assemblages in interior Atlantic Forest and cerrado regions of southeastern Brazil are impoverished, since we found lower richness and abundance of different groups in landscapes with lower amounts of forest. The relatively higher threshold value of 47% suggests that bat communities have a relatively lower resistance to habitat degradation than other animal groups. Accordingly, conservation and restoration strategies should focus on increasing the amount of native vegetation of landscapes so as to enhance species richness of bats.

The understory bat community in a fragmented landscape in the lowlands of the Los Tuxtlas, Veracruz, Mexico

“…It remains uncertain, however, as to how much if any of this taxonomic bias has been modulated by the forest fragmentation in the surrounding areas. Similar results have been reported for rainforests and tropical dry forests in Mexico andBrazil (Avila-Cabadilla et al 2009, 2014;Lim and Tavares 2012;De la Peña et al 2012;Vleut et al 2012Vleut et al , 2013Muylaert et al 2016).…”

“…La comu-habitat fragmentation in the northwest portion of the Los Tuxtlas region on mammals, birds and plants are well documented (Estrada et al 1993;Coates-Estrada 2001a, Estrada andCoates-Estrada 2002;Galindo and Sosa 2003;Galindo 2004, Aguirre andDirzo 2008;Arroyo et al 2012). In the case of bats, studies in other areas have found that forest fragmentation tends to reduce the abundance of certain species and has an overall negative effect on species diversity (Medellín et al 2000;Farneda et al 2015;Muylaert et al 2016).…”

Implications of vegetation clearing biases for the interpretation of landscape-scale species-area relationships

“…Notably, Lima and Mariano-Neto (2014) highlighted a lack of correlation between soil fertility and forest area, thereby excluding biased clearing as a confounding factor in their identification of a threshold in the relationship between forest tree species richness and landscape-scale forest cover in the Atlantic Forest of Brazil. Yet, the potential for the confounding effect of non-random patterns of vegetation clearing to bias these observed relationships remains largely unacknowledged (Estavillo et al, 2013;Morante-Filho et al, 2015;Ochoa-Quintero et al, 2015;Richmond et al, 2015;Muylaert et al, 2016). Given the conjecture about the threshold concept for informing management, my research emphatically supports Maron et al's (2012) message that biased clearing patterns should be a central consideration in the examination of area effects in modified landscapes.…”

“…In a study on the response of forest-specialist mammals to habitat loss in the Atlantic Forest of Brazil, Estavillo et al (2013) reported that a rapid decline in species richness was observed in landscapes with less than 30% forest cover. In other studies from the Atlantic Forest, thresholds of landscape-scale forest cover below which species richness exhibited a sharp decline were observed at approximately 30-50% for birds (Martensen et al, 2012), 50% for forest-specialist birds (Morante-Filho et al, 2015), 47% for bats (Muylaert et al, 2016), 30% for forest trees of the family Sapotaceae ) and 10-30% for small mammals . Richmond et al (2015) noted a broad range in observed thresholds in the relationship between forest bird richness and different types of landscape-scale forest cover in two regions of Canada.…”

Spatial variation of bat diversity between three floodplain-savanna ecosystems of the Colombian Llanos

“…It has been found that bat assemblages show a low resilience to habitat loss in Cerrado savannas, where a drop in richness and diversity levels has been observed (Muylaert et al 2016). Despite the conflicting results about the effect of deforestation on the reduction of forest cover, habitat loss and transformation, and fragmentation in bat diversity (Coutinho and Bernard 2012), it has been found that the structure of bat assemblages may be dominated by a smaller number of species in areas showing a higher deforestation rate (Fenton et al 1992;Reis and Müller 1995;Brosset et al 1996;Cosson et al 1999;Faria 2006).…”