Signal and Noise in Biodiversity Dynamics

Jeremy Beaulieu, University of Arkansas, USA 

Across a variety of biological datasets, from genomes to conservation to the fossil record, evolutionary rates appear to increase toward the present or over short time scales. This has long been seen as an indication of processes operating differently at different time scales, even potentially as an indicator of a need for new theory connecting macroevolution and microevolution. Here I introduce a set of models that assess the relationship between rate and time and demonstrate that these patterns are statistical artifacts of time-independent errors present across ecological and evolutionary datasets, which produce hyperbolic patterns of rates through time. I will show that plotting a noisy numerator divided by time versus time leads to the observed hyperbolic pattern; in fact, randomizing the amount of change over time generates patterns functionally identical to observed patterns. Ignoring noise will not only obscure true patterns but create novel patterns that have long misled scientists. I will also briefly discuss the need for a broader term for noise (i.e., tip fog), and then present new methods for dealing with tip fog in a variety of phylogenetic comparative methods, even when the underlying variation is not actually measured.

From Persistence to Speed: Evolutionary Shifts to Annual Life Cycles in Pooideae

Siri Fjellheim, Norwegian University of Life Sciences, Norway

Annuality—the completion of a life cycle within a single year—has evolved repeatedly within the grass subfamily Pooideae. These recurrent transitions suggest that certain lineages carry evolutionary precursors that facilitate shifts from perennial persistence to rapid, semelparous reproduction. Comparative studies indicate that traits related to growth rates, biomass allocation, and developmental timing may be central to these transitions. To explore this further, we have investigated annual–perennial species pairs across Pooideae, focusing on vegetative and reproductive development. In particular, we examine growth strategies between annual and perennial species pairs, as well as branching and flowering architecture as key determinants of whether plants maintain vegetative meristems for future growth or commit entirely to reproduction. Our results do not only advance our understanding of life history evolution but also provide a foundation for considering how growth habit might be reconfigured in crops.

Use of multiple sources of evidence to identify and localize climate refugia: a case study from the Cape Floristic Region of South Africa

G. Anthony Verboom, University of Gothenburg, Sweden

While the Cape Floristic Region (CFR) of South Africa is believed to have enjoyed a generally stable climate through the Pliocene-Pleistocene, the western CFR is believed to have been more stable than the east, this stability fostering reduced extinction and so accounting for the greater species richness there. To test this hypothesis, we examined multiple proxies, including the species richness-environment heterogeneity relationship, palaeo-endemism patterns, biased ancestral area inference, historical dispersal pathways, and patterns of population genetic diversity. The patterns revealed by these lines of evidence display considerable consilience, with the mountains of the southwestern CFR being resolved as a long-term climatic refugium. This area is characterized by complex relief and geology which, together with a saturating winter precipitation regime, underpins the emergence of a system of groundwater-fed habitats and a rich flora of moisture-dependent plant species. Ongoing abstraction of water in this area threatens the long-term persistence of fynbos plant diversity.