Long-term Isopropanol Storage Does Not Alter Fish Morphometrics

Information from natural history collections (NHCs) about the diversity, taxonomy and historical distributions of species worldwide is becoming increasingly available over the Internet. In light of this relatively new and rapidly increasing resource, we critically review its utility and limitations for addressing a diverse array of applications. When integrated with spatial environmental data, NHC data can be used to study a broad range of topics, from aspects of ecological and evolutionary theory, to applications in conservation, agriculture and human health. There are challenges inherent to using NHC data, such as taxonomic inaccuracies and biases in the spatial coverage of data, which require consideration. Promising research frontiers include the integration of NHC data with information from comparative genomics and phylogenetics, and stronger connections between the environmental analysis of NHC data and experimental and field-based tests of hypotheses.

Understanding how and why certain clades diversify greatly in morphology whereas others do not remains a major theme in evolutionary biology. Projecting families of phylogenies into multivariate morphospaces can distinguish two scenarios potentially leading to unequal morphological diversification: unequal magnitude of change per phylogenetic branch, and unequal efficiency in morphological innovation. This approach is demonstrated using a case study of skulls in sister clades within the South American fish superfamily Anostomoidea. Unequal morphological diversification in this system resulted not from the morphologically diverse clade changing more on each phylogenetic branch, but from that clade distributing an equal amount of change more widely through morphospace and innovating continually. Although substantial morphological evolution occurred throughout the less diverse clade's history, most of that clade's expansion in morphospace occurred in the most basal branches, and more derived portions of that radiation oscillated within previously explored limits. Because simulations revealed that there is a maximum 2.7% probability of generating two clades that differ so greatly in the density of lineages within morphospace under a null Brownian model, the observed difference in pattern likely reflects a difference in the underlying evolutionary process. Clade-specific factors that may have promoted or arrested morphological diversification are discussed.