Defining plant ecological specialists and generalists: Building a framework for identification and classification

Alex Kirsch, Ecology, Evolution & Behavior, Minnesota State University, Mankato, Mankato, MN and Matthew A. Kaproth, Ecology, Evolution & Behavior, University of Minnesota, Mankato, Mankato, MN

Background/Question/Methods
Ecological specialization is a widespread concept in biological fields and studies. However, usage of the terminology has become problematic due to ambiguity and variance. While some have argued that specialization can never be truly classified, here we attempt to do exactly that using Quercus as a study system. Here, specialization and generalization are defined as a spectrum, and 150 Quercus species are ranked for their degree of specialization using metrics identified as being relevant to the concept (habitat diversification, intraspecific functional leaf trait plasticity, interspecies symbioses). These rankings were then correlated to two additional data sets to make inferences about specialization terminology used in practice. Firstly, rankings were compared to each species’ IUCN Red list designation, as specialist species are thought to be more threatened by disturbance. Correlation should be high, as species identified as specialists should be more often threatened. The second data set consists of the results of a specialization survey sent to scientists familiar with Quercus. Scientists were asked to identify how specialized each species is (only for species they are familiar with). Correlation between rankings and these data should be high if there is truly consistency in the usage of the terms in practice.
Results/Conclusions
Ordinal logistic regression between quantified specialization rankings of each species and their respective IUCN designation shows that an increase in specialization score is positively tied to an IUCN designation that is more threatened (X = 6.255, p = 0.0124). Our data indicates that highly threatened Quercus species are largely specialized compared to most Quercus species. From this result we conclude that specialization can be measured objectively with accessible metrics, and that species identified as specialized should be given a higher priority when it comes to utilizing conservation resources. These rankings would also allow us to investigate systematics questions such as ‘How does specialization emerge within a clade?’ and ‘What is the inheritance pattern for specialization strategies?’.