Résumé
Aim: Phenology of a wide diversity of organisms has a dependency on
climate, usually with reproductive periods beginning earlier in the year
and lasting longer at lower latitudes. Temperature and day length are
known environmental drivers of the reproductive timing of many species.
Hence, reproductive phenology is sensitive to warming and is important to
be considered for reliable predictions of species distributions. This is
particularly relevant for rapidly spreading non-indigenous species (NIS).
In this study, we forecast the future ranges of a NIS, the seaweed
Sargassum muticum, including its reproductive phenology. Location: Coastal
areas of the Northern Hemisphere (Pacific and Atlantic oceans). Methods:
We used ecological niche modelling to predict the distribution of S.
muticum under two scenarios forecasting limited (RCP 2.6) and severe (RCP
8.5) future climate changes. We then refined our predictions with a hybrid
model using sea surface temperature constraints on reproductive phenology.
Results: Under the most severe climate change scenario, we predicted
northward expansions which may have significant ecological consequences
for subarctic coastal ecosystems. However, in lower latitudes, habitats
currently occupied by S. muticum will no longer be suitable, creating
opportunities for substantial community changes. The temperature
constraints imposed by the reproductive window were shown to restrict the
modelled future species expansion strongly. Under the RCP 8.5 scenario,
the total range area was expected to increase by 61.75 % by 2100, but only
by 1.63 % when the reproductive temperature window was considered. Main
conclusions: Altogether these results exemplify the need to integrate
phenology better to improve the prediction of future distributional shifts
at local and regional scales.