Cryptic species could represent a substantial fraction of biodiversity. However, inconsistent definitions and taxonomic treatment of cryptic species prevent informed estimates of their contribution to biodiversity and impede our understanding of their evolutionary and ecological significance. We propose a conceptual framework that recognizes cryptic species based on their low levels of phenotypic (morphological) disparity relative to their degree of genetic differentiation and divergence times as compared with non-cryptic species. We discuss how application of a more rigorous definition of cryptic species in taxonomic practice will lead to more accurate estimates of their prevalence in nature, better understanding of their distribution patterns on the tree of life, and increased abilities to resolve the processes underlying their evolution.

The temporal dynamics of species diversity are shaped by variations in the rates of speciation and extinction, and there is a long history of inferring these rates using first and last appearances of taxa in the fossil record. Understanding diversity dynamics critically depends on unbiased estimates of the unobserved times of speciation and extinction for all lineages, but the inference of these parameters is challenging due to the complex nature of the available data. Here, we present a new probabilistic framework to jointly estimate species-specific times of speciation and extinction and the rates of the underlying birth-death process based on the fossil record. The rates are allowed to vary through time independently of each other, and the probability of preservation and sampling is explicitly incorporated in the model to estimate the true lifespan of each lineage. We implement a Bayesian algorithm to assess the presence of rate shifts by exploring alternative diversification models. Tests on a range of simulated data sets reveal the accuracy and robustness of our approach against violations of the underlying assumptions and various degrees of data incompleteness. Finally, we demonstrate the application of our method with the diversification of the mammal family Rhinocerotidae and reveal a complex history of repeated and independent temporal shifts of both speciation and extinction rates, leading to the expansion and subsequent decline of the group. The estimated parameters of the birth-death process implemented here are directly comparable with those obtained from dated molecular phylogenies. Thus, our model represents a step towards integrating phylogenetic and fossil information to infer macroevolutionary processes.

The question ‘what renders a species extinction prone’ is crucial to biologists. Ecological specialization has been suggested as a major constraint impeding the response of species to environmental changes. Most neoecological studies indicate that specialists suffer declines under recent environmental changes. This was confirmed by many paleoecological studies investigating longer-term survival. However, phylogeneticists, studying the entire histories of lineages, showed that specialists are not trapped in evolutionary dead ends and could even give rise to generalists. Conclusions from these approaches diverge possibly because (i) of approach-specific biases, such as lack of standardization for sampling efforts (neoecology), lack of direct observations of specialization (paleoecology), or binary coding and prevalence of specialists (phylogenetics); (ii) neoecologists focus on habitat specialization; (iii) neoecologists focus on extinction of populations, phylogeneticists on persistence of entire clades through periods of varying extinction and speciation rates; (iv) many phylogeneticists study species in which specialization may result from a lack of constraints. We recommend integrating the three approaches by studying common datasets, and accounting for range-size variation among species, and we suggest novel hypotheses on why certain specialists may not be particularly at risk and consequently why certain generalists deserve no less attention from conservationists than specialists.

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Tropical forests are being lost at an alarming rate. Studies from various tropical locations report losses of forest birds as possibly direct or indirect results of deforestation. Although it may take a century for all the sensitive species to be extirpated from a site following habitat loss, species with larger or heavier bodies and those foraging on insects, fruits, or both are particularly extinction prone. Larger-or heavier-bodied species may occur at low densities, increasing their vulnerability to habitat alterations. Insectivores are vulnerable for reasons such as the loss of preferred microhabitats, poor dispersal abilities, and/or ground nesting habits that make them susceptible to predation. The lack of year-round availability of fruits may make survival in deforested or fragmented areas difficult for frugivores. Extirpation of large predators, superior competitors, pollinators, and seed dispersers may have repercussions for tropical ecosystem functioning. Large tropical reserves that adequately protect existing forest avifauna are needed. Sound ecological knowledge of tropical forest avifauna for biodiversity-friendly forest management practices is also needed but sorely lacking.

Summary1. Priority question exercises are becoming an increasingly common tool to frame future agendas in conservation and ecological science. They are an effective way to identify research foci that advance the field and that also have high policy and conservation relevance. 2. To date, there has been no coherent synthesis of key questions and priority research areas for palaeoecology, which combines biological, geochemical and molecular techniques in order to reconstruct past ecological and environmental systems on time-scales from decades to millions of years. 3. We adapted a well-established methodology to identify 50 priority research questions in palaeoecology. Using a set of criteria designed to identify realistic and achievable research goals, we selected questions from a pool submitted by the international palaeoecology research community and relevant policy practitioners. 4. The integration of online participation, both before and during the workshop, increased international engagement in question selection. 5. The questions selected are structured around six themes: human-environment interactions in the Anthropocene; biodiversity, conservation and novel ecosystems; biodiversity over long time-scales; ecosystem processes and biogeochemical cycling; comparing, combining and synthesizing information from multiple records; and new developments in palaeoecology. 6. Future opportunities in palaeoecology are related to improved incorporation of uncertainty into reconstructions, an enhanced understanding of ecological and evolutionary dynamics and processes and the continued application of long-term data for better-informed landscape management. 256-26750 priority research questions in palaeoecology 257 7. Synthesis. Palaeoecology is a vibrant and thriving discipline, and these 50 priority questions highlight its potential for addressing both pure (e.g. ecological and evolutionary, methodological) and applied (e.g. environmental and conservation) issues related to ecological science and global change.

Knowing the geographic extents of species is crucial for understanding the causes of diversity distributions and modes of speciation and extinction. Species geographic ranges are often viewed as approximately constant in size in geological time, even though climate change studies have shown that historical and modern species geographic distributions are not static. Here, we use an extensive global microfossil database to explore the temporal trajectories of geographic extents over the entire lifespan of marine nannoplankton, diatom, planktic foraminifer and radiolarian species. We show that geographic extents are not static over geological time-scales. Temporal trajectories of species geographic ranges are asymmetric: the rise is quicker than the fall. We propose that once a species has overcome its initial difficulties in geographic establishment, it rises to its peak geographic extent. However, once this peak value is reached, it will also have a maximal number of species to interact with. The negative of these biotic interactions could then cause a gradual geographic decline. We discuss the multiple implications of our findings with reference to macroecological and macroevolutionary studies.

Do large mammals evolve faster than small mammals or vice versa?Because the answer to this question contributes to our understanding of how life-history affects long-term and large-scale evolutionary patterns, and how microevolutionary rates scale-up to macroevolutionary rates, it has received much attention. A satisfactory or consistent answer to this question is lacking, however. Here, we take a fresh look at this problem using a large fossil dataset of mammals from the Neogene of the Old World (NOW). Controlling for sampling biases, calculating per capita origination and extinction rates of boundary-crossers and estimating survival probabilities using capture-mark-recapture (CMR) methods, we found the recurring pattern that large mammal genera and species have higher origination and extinction rates, and therefore shorter durations. This pattern is surprising in the light of molecular studies, which show that smaller animals, with their shorter generation times and higher metabolic rates, have greater absolute rates of evolution. However, higher molecular rates do not necessarily translate to higher taxon rates because both the biotic and physical environments interact with phenotypic variation, in part fueled by mutations, to affect origination and extinction rates. To explain the observed pattern, we propose that the ability to evolve and maintain behavior such as hibernation, torpor and burrowing, collectively termed ''sleep-orhide'' (SLOH) behavior, serves as a means of environmental buffering during expected and unexpected environmental change. SLOH behavior is more common in some small mammals, and, as a result, SLOH small mammals contribute to higher average survivorship and lower origination probabilities among small mammals.body size ͉ environmental buffering ͉ metabolism ͉ Neogene mammals ͉ turnover E volution operates at different scales of time and levels of the biological hierarchy (1). Body size covaries with many individual and species level traits (2), each of which could influence the tempo of evolution at population, species and clade levels. Multiple studies have shown that smaller sized mammals have higher molecular rates of evolution in absolute time, possibly because of a generation time effect and/or metabolic rate effect (3-8). Higher molecular rates may translate to higher rates of phenotypic changes (9 but see 10, 11) and a greater chance of reproductive isolation, which could ultimately lead to higher speciation rates (12) and higher rates of pseudoextinction, which could be observed as higher extinction rates among fossil taxa. As such, small mammals could be expected to have higher origination and extinction rates as observed in the fossil record. However, empirical studies on historical extinctions show that large mammals are at higher risk of extinction and have been selectively removed (13-17), as is also indicated by the Pleistocene megafauna extinction literature (18,19), even though body size per se may not always be a good predictor of extinction risk (20)(21)(22). Neither ...