[PCA] ARTICLE: Germination niche breadth varies inconsistently among three Asclepias congeners along a latitudinal gradient

[De Angelis, Patricia]

J. Finch;  J. L. Walck;  S. N. Hidayati;  A. T. Kramer;  V. Lason;  K.
Havens

ABSTRACT: Species responses to climate change will be primarily driven by
their environmental tolerance range, or niche breadth, with the expectation
that broad niches will increase resilience. Niche breadth is expected to be
larger in more heterogeneous environments and moderated by life history.
Niche breadth also varies across life stages. Therefore, the life stage
with the narrowest niche may serve as the best predictor of climatic
vulnerability. To investigate the relationship between niche breadth,
climate and life stage we identify germination niche breadth for dormant
and non‐dormant seeds in multiple populations of three milkweed (Asclepias)
species.
Complementary trials evaluated germination under conditions simulating
historic and predicted future climate by varying cold–moist stratification
temperature, length and incubation temperature. Germination niche breadth
was derived from germination evenness across treatments (Levins Bn), with
stratified seeds considered less dormant than non‐stratified seeds.

Germination response varies significantly among species, populations and
treatments. Cold–moist stratification ≥4 weeks (1–3 °C) followed by
incubation at 25/15 °C+ achieves peak germination for most populations.
Germination niche breadth significantly expands following stratification
and interacts significantly with latitude of origin. Interestingly, two
species display a positive relationship between niche breadth and latitude,
while the third presents a concave quadratic relationship.
Germination niche breadth significantly varies by species, latitude and
population, suggesting an interaction between source climate, life history
and site‐specific factors. Results contribute to our understanding of
inter‐ and intraspecific variation in germination, underscore the role of
dormancy in germination niche breadth, and have implications for
prioritising and conserving species under climate change.

Full article: https://onlinelibrary.wiley.com/doi/abs/10.1111/plb.12843
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