Individual dispersal, landscape connectivity and ecological networks

Abstract

Connectivity is classically considered an emergent property of landscapes encapsulating individuals' flows across space. However, its operational use requires a precise understanding of why and how organisms disperse. Such movements, and hence landscape connectivity, will obviously vary according to both organism properties and landscape features. We review whether landscape connectivity estimates could gain in both precision and generality by incorporating three fundamental outcomes of dispersal theory. Firstly, dispersal is a multi-causal process; its restriction to an 'escape reaction' to environmental unsuitability is an oversimplification, as dispersing individuals can leave excellent quality habitat patches or stay in poor-quality habitats according to the relative costs and benefits of dispersal and philopatry. Secondly, species, populations and individuals do not always react similarly to those cues that trigger dispersal, which sometimes results in contrasting dispersal strategies. Finally, dispersal is a major component of fitness and is thus under strong selective pressures, which could generate rapid adaptations of dispersal strategies. Such evolutionary responses will entail spatiotemporal variation in landscape connectivity. We thus strongly recommend the use of genetic tools to: (i) assess gene flow intensity and direction among populations in a given landscape; and (ii) accurately estimate landscape features impacting gene flow, and hence landscape connectivity. Such approaches will provide the basic data for planning corridors or stepping stones aiming at (re)connecting local populations of a given species in a given landscape. This strategy is clearly species- and landscape-specific. But we suggest that the ecological network in a given landscape could be designed by stacking up such linkages designed for several species living in different ecosystems. This procedure relies on the use of umbrella species that are representative of other species living in the same ecosystem.

The impact of a small-scale riverine obstacle on the upstream migration of Atlantic Salmon

“…The loss and fragmentation of habitat truncate movement, reduce connectivity, and often precede the decline and extirpation of a species (Ceballos & Ehrlich, 2002;Baguette et al, 2013). In rivers, habitat connectivity is primarily longitudinal and in general confined to the river corridor.…”

Biological Correlates of Extinction: What Does Differentiate Survivors From Victims?

“…In addition, dispersal ability is commonly positively correlated to geographic range size (NOGUÉS-BRAVO et al, 2014). Species with low dispersal ability also tend to have highly fragmented, small populations (BAGUETTE et al, 2013).…”

“…Since then, geologists, paleontologists and biologists have widely improved the understanding of how and why the individuals of a species can be terminated locally, regionally or globally (i.e. completely extinct) (PURVIS et al, 2000a(PURVIS et al, , 2000bBAGUETTE et al, 2013). Paleontological records indicate that all species of whole genera, families and orders became extinct throughout geological time (e.g.…”

Rural avenues as dispersal corridors for the vulnerable saproxylic beetle Elater ferrugineus in a fragmented agricultural landscape

“…those dispersal events that contribute to gene flow (Guerriero et al 2011). The influence of landscape structure on effective dispersal could be determined by developing resistance surfaces-spatial models, in which specific landscape features are translated into likely costs of dispersal for the organism under study Zeller et al 2012;Baguette et al 2013). Habitat models can be used to calculate the among-individuals distances corrected for dispersal costs (the socalled 'effective distances'), and tested by correlating calculated distances with genetic similarity between individuals .…”