Saturday, October 19, 2013

Climate Change, Phenology and Niche

One of the fundamental questions that ecologist ask is "what are the physical conditions that enable species co-existence?" or alternatively "what are the physical conditions that enable species dominance?" Ecologist often use the fundamental niche to describe conditions that a species is suited, and the realized niche to describe the locations  (or conditions) where the species is actually observed.

Rapidly changing temperatures are causing a bit of a stir. Many plants and animals life-histories are tightly controlled or coupled with environmental conditions. For instance,  you may have noticed that years with warmer springs often bring earlier blossoming of cherry trees. Not all plants and animals respond to higher temperatures in the same way, some species' phenology (or timing of a life history event) may be tightly coupled with temperature while others less so. Large scale variation in temperatures can thus alter the relative timing of phenology between two species. If one of these species is dependent on the other for food this can be a bad thing for species B. Climate change can not only influence the relationship between predator and prey it can also change the amount of apparent competition between sets of species.

In a paper I have recently published, I showed that higher temperature can lead to less niche overlap between species in the southern New England benthic community, specifically the "fouling community". The fouling community is compose of animals like tunicates, mussels, barnacles and bryozoans that compete for space on hard substrates like subtidal boulders. Niche overlap has been used as a proxy for competition between species within a community. Lower niche overlap may be a result of earlier recruitment driven by temperature. Higher temperatures effectively make more time available for species in the community to recruit. With more time available for recruitment this may mean that there is less competition for some species during there periods of recruitment.

One interesting pattern that we observed during this study is that more recent invasive species tend to recruit latter in the year. Another way to way this is that the the timing of recruitment of invasive species is correlated to there relative time of there historical invasion into southern New England. The reasons for this pattern are not quite clear but this may be a case of species evolving earlier recruitment.