4.2 Niche overlap analysis
New England and eastern cottontail had unusually high niche overlap and
low niche differentiation for two species. Niche overlap analyses with
other species have found a mix of both high and low niche overlap (Liu
et al. 2017, Pascual-Rico et al. 2020, Quiroga and Souto 2022), but few
studies with two mammalian species have found similarly high niche
overlap values and low proportions of the native species niche not
overlapping with the introduced species niche. Although New England and
eastern cottontail niches were highly similar, they were not equivalent.
The lack of equivalency suggests outside conditions or pressures may
influence the prevalence of eastern cottontail across the state despite
high niche overlap with New England cottontail.
One possible mechanism for the high observed overlap in environmental
space, but not geographic space, is competition. Previous studies have
identified competition between the two species and supported eastern
cottontail as the dominant competitor (Probert and Litvaitis 1996,
Cheeseman et al. 2018, Bischoff et al. 2023b ). Competition
between New England and eastern cottontail was first observed in
behavioral studies but lacked evidence of interference competition
(Probert and Litvaitis 1996). A resource selection study of
radio-tracked individuals associated interspecific competition with
displacement of New England cottontail from young forest and shrubland
habitat (Cheeseman et al. 2018). Relative abundance studies further
supported interspecific competition, where patches with high numbers of
eastern cottontail had lower New England cottontail abundance (Bischoff
et al. 2023b ). A rigorous experimental test of New England
cottontail-eastern cottontail competition, during all seasons and parts
of the annual life cycle, would confirm the mechanism(s) and provide
insight into paths for New England cottontail conservation in the
continued face of eastern cottontail range expansion.