Variations in risk-taking behaviour mediate matrix mortality's impact on biodiversity under fragmentation

The impact of fragmentation on biodiversity is driven by more than the
spatial configuration of suitable habitat patches. Habitat is embedded in
the surrounding anthropogenic land cover, known as the matrix, which plays
a key role in species movement and connects the fragmented habitat.
Whether the matrix is a barrier or a conduit to movement depends on the
mortality of the moving individuals. However, individuals differ in their
behavioural response to the risk posed by the matrix, with the willingness
to enter the matrix depending on an individual's risk-taking
behaviour. This individual-level behavioural variability is rarely
considered but represents an additional mechanism shaping inter- and
intraspecific competition as well as evolutionary behavioural responses.
We used an individual-based model to scale up from individual foraging
movements to the resulting community structure of a competitive small
mammal community in differently fragmented landscapes. The model
interactively considers extrinsic matrix conditions, given a certain
mortality rate, and individual differences in intrinsic movement decisions
when moving into the matrix. The model was used to investigate the
consequences of fragmentation and matrix mortality for species and
behavioural diversity. Low matrix mortality resulted in a positive effect
of fragmentation on species diversity. At the same time, it led to a high
average risk-taking behaviour. While this was an important adaptive
response to fragmentation, it also led to a loss of intraspecific
diversity. High matrix mortality reversed the effect of fragmentation,
leading to a drastic loss of species with increasing fragmentation. High
mortality risk reduced average risk-taking, especially at high
fragmentation. Study findings suggest that the feasibility of movement in
the matrix can influence species diversity and evolutionary responses of
movement-related behavioural traits in fragmented landscapes. The matrix
may thus play a key role in reconciling contrasting empirical results and
provides a promising tool for future biodiversity conservation.