4.2. Climate niche divergence/conservatism
The current investigation, employing niche dynamic analysis, has
revealed a noteworthy phenomenon regarding the climatic niche of two
species, thereby affirming the concept of niche conservatism (Xian et
al., 2023). The niche equivalency test, as applied, demonstrates that
the observed overlap in niche characteristics between the two species is
more pronounced than expected under random assignment, thus shedding
light on the transferability of their climatic niche (Sillero et al.,
2022). Notably, the observed overlap in the niche similarity test, while
notably more significant than that expected by random assignment or
simulation, did not attain statistical significance. Gallego‐Narbón et
al. (2023) elucidated that a scenario where the observed overlap is
relatively high and the similarity test remains non-significant
indicates geographical proximity between the species pairs. This
reinforces the outcomes of our study, illustrating that these species
are not identical but share similarities within their environmental
habitat and are indeed geographically proximate.
The presence of stringent criteria for expansion and high stability
criteria point towards these species displaying non-aggressive behavior,
with their native niche exhibiting stability and a limited ability to
adapt to novel environmental conditions. In simpler terms, these species
exhibit fidelity to their existing climatic conditions, actively seeking
niches that mirror historical climates (Wang et al., 2023). Our findings
align with those of Lustenhouwer & Parker (2022), where the niche
conservatism hypothesis remains unchallenged, marked by low expansion
criteria and a predominance of niche stability. Furthermore, niche
unfilling is evident, with the species utilizing less than half of the
available environmental space, contingent on their dispersal
capabilities (Keppel et al., 2012). It is imperative to identify areas
less susceptible to climate change, called climate macro-refugia, due to
the escalating pace of climate change.
Given the conserved nature of
these species’ climatic niche and their limited adaptability to new
climatic conditions, their occurrence is confined to habitats resembling
their ancestral or native ranges. Considering the regional topography,
physiological and phenological traits, and the constrained seed
dispersal resulting from the seeds’ substantial weight, it can be
reasonably concluded that these species exhibit limited spatial and
temporal transfer capabilities. Consequently, they are highly vulnerable
to the impacts of climate change, lacking the natural ability to migrate
to habitats projected by species distribution models.