Effects of habitat area and spatial configuration on biodiversity in an experimental intertidal community

Abstract

Isolating the effects of fragmentation per se (i.e., spatial configuration of habitat patches) on species richness is an ongoing challenge as habitat configuration often covaries with the amount of habitat. Consequently, there is a lack of experimental evidence for configurational effects on species richness in the whole landscape. Here, we developed a novel experimental system for testing the independent and interactive effects of habitat area and configuration on tropical intertidal species richness. Our results confirmed the expectation that average species richness would increase monotonically with habitat area. More intriguingly, we found mixed evidence for a non‐monotonic relationship between species richness and fragmentation per se, with the highest richness at intermediate fragmentation configuration, that is, when habitat tiles were placed in a “several‐small” configuration. The effect of habitat configuration was not due to passive sampling (since area was controlled for), variation in total individual abundance, or niche specialization of species to different landscape configurations. We postulate that a combination of processes, including local negative density dependence and dispersal limitation, could give rise to the observed pattern. We emphasize the importance of considering configurational effects on biodiversity at broader spatial scales and for more experimental research to delve into the mechanisms driving the patterns seen here.

Habitat fragmentation and species diversity in competitive communities

“…While real communities arguably are more complex, we observe that even under these simplistic assumptions habitat fragmentation can influence species richness in multitude of ways: fragmentation per se can show both negative and positive effects on species richness in competitive metacommunities, and intermediate levels of fragmentation may sometimes positively influence species richness. Interestingly, the non-monotone patterns similar to those predicted by our model were recently been observed in an experimental fragmentation study (Loke et al 2019).…”

“…Interestingly, the non‐monotone patterns similar to those predicted by our model were recently been observed in an experimental fragmentation study (Loke et al . ).…”

“…; Loke et al . ) depending on the species' traits together with structure of the habitat (e.g. degree of spatial autocorrelation in habitat types).…”

“…generalists and edge species) (Henle et al 2004). When considering community-level properties, such as species richness, both theoretical and empirical studies have observed that different spatial configurations of the habitat can have both negative and positive effects on species richness (Tilman et al 1997;Hanski et al 2013;Hanski 2015;Haddad et al 2015;Fahrig 2017;Thompson et al 2017;Haddad et al 2017;Loke et al 2019) depending on the species' traits together with structure of the habitat (e.g. degree of spatial autocorrelation in habitat types).…”

Towards an urban marine ecology: characterizing the drivers, patterns and processes of marine ecosystems in coastal cities

“…Dispersal limitation can therefore also interact with local stressors and abiotic conditions to result in compositionally very different assemblages across patches of hard substrata (Bulleri andChapman 2004, Munari 2013). This may be accentuated where urban habitat conversion has significantly altered hydrodynamic patterns, created other additional barriers to dispersal and subsequent settlement (Bishop et al 2017) or changed the configuration of habitats at the landscape scale (Loke et al 2019c).…”