Our understanding of the evolution of social mating systems is largely based on an atemporal ecological framework, whereas macroevolutionary and phylogenetic perspectives looking at the causes of mating systems variation are less developed. Here, we present analyses of the evolution of social mating systems in birds at an unprecedented scale, including 66% of the world\'s birds and using trait-dependent speciation and extinction models. We found that lekking (no social bond between the sexes) is very rarely lost, in accordance with the hypothesis that a male shifting to investing in one rather than multiple mates would suffer a severe fitness cost. In contrast, resource-defense polygamous lineages (with a weak, transient socio-sexual bond) frequently revert back to monogamy (strong, durable socio-sexual bond) and have an elevated extinction fraction. We tentatively attribute this to the impossibility for females to settle on an optimal parental care strategy under this system. Finally, we found that most gains of lekking have been directly from monogamy, rather than through an intermediate stage of resource-defense polygamy.

Every organism interacts with a host of other organisms of the same and different species throughout its life. These biotic interactions have varying influences on the reproduction and dispersal of the organism, and hence also the population and species lineage to which the organism belongs. By extension, biotic interactions must contribute to the macroevolutionary patterns that we observe in the fossil record, but exactly how, when and why are research questions we have been asking before the start of the journal Paleobiology. In this contribution for Paleobiology\'s 50th anniversary, we present a brief overview of how paleobiologists have studied biotic interactions and their macroevolutionary consequences, recognizing paleontology\'s unique position to contribute data and insights to the topic of interspecies interactions. We then explore, in a semi free-form manner, what promising avenues might be open to those of us who use the fossil record to understand biotic interactions. In general, we emphasize the need for an increased effort in the understanding of ecological details, the integration of different types of information, and to strive for model-based approaches.

The relationship between the evolutionary dynamics observed in contemporary populations (microevolution) and evolution on timescales of millions of years (macroevolution) has been a topic of considerable debate. Historically, this debate centers on inconsistencies between microevolutionary processes and macroevolutionary patterns. Here, we characterize a striking exception: emerging evidence indicates that standing variation in contemporary populations and macroevolutionary rates of phenotypic divergence are often positively correlated. This apparent consistency between micro- and macroevolution is paradoxical because it contradicts our previous understanding of phenotypic evolution and is so far unexplained. Here, we explore the prospects for bridging evolutionary timescales through an examination of this \"paradox of predictability.\" We begin by explaining why the divergence-variance correlation is a paradox, followed by data analysis to show that the correlation is a general phenomenon across a broad range of temporal scales, from a few generations to tens of millions of years. Then we review complementary approaches from quantitative-genetics, comparative morphology, evo-devo, and paleontology to argue that they can help to address the paradox from the shared vantage point of recent work on evolvability. In conclusion, we recommend a methodological orientation that combines different kinds of short-term and long-term data using multiple analytical frameworks in an interdisciplinary research program. Such a program will increase our general understanding about how evolution works within and across timescales.

Diet has been identified as a major driver of reef fish lineage diversification, producing one of the most speciose vertebrate assemblages today. Yet, there is minimal understanding of how, when and why diet itself has evolved. To address this, we used a comprehensive gut content dataset, alongside a recently developed phylogenetic comparative method to assess multivariate prey use across a diverse animal assemblage, coral reef fishes. Specifically, we investigated the diversification, transitions and phylogenetic conservatism of fish diets through evolutionary time. We found two major pulses of diet diversification: one at the end-Cretaceous and one during the Eocene, suggesting that the Cretaceous-Palaeogene mass extinction probably provided the initial ecological landscape for fish diets to diversify. The birth of modern families during the Eocene then provided the foundation for a second wave of dietary expansion. Together, our findings showcase the role of extinction rebound events in shaping the dietary diversity of fishes on present-day coral reefs.

Nutrient foramina are small openings in the periosteal surface of the mid-shaft region of long bones that traverse the cortical layer and reach the medullary cavity. They are important for the delivery of nutrients and oxygen to bone tissue and are crucial for the repair and remodeling of bones over time. The nutrient foramina in the femur\'s diaphysis are related to the energetic needs of the femur and have been shown to be related to the maximum metabolic rate (MMR) of taxa. Here, we investigate the relationship between nutrient foramen size and body mass as a proxy to the aerobic capacity of taxa in living and extinct xenarthrans, including living sloths, anteaters, and armadillos, as well as extinct xenarthrans such as glyptodonts, pampatheres, and ground sloths. Seventy femora were sampled, including 20 from extant taxa and 50 from extinct taxa. We obtained the blood flow rate (Q̇) based on foramina area and performed PGLS and phylogenetic ANCOVA in order to explore differences among mammalian groups. Our results show that, among mammals, taxa commonly associated with lower metabolism like living xenarthrans showed relatively smaller foramina, while the foramina of giant extinct xenarthrans like ground sloths and glyptodonts overlapped with non-xenarthran placentals. Consequently, Q̇ estimations indicated aerobic capacities comparable to other placental giant taxa like elephants or some ungulates. Furthermore, the estimation of the MMR for fossil giant taxa showed similar results, with almost all taxa showing high values except for those for which strong semi-arboreal or fossorial habits have been proposed. Moreover, the results are compatible with the diets predicted for extinct taxa, which indicate a strong consumption of grass similar to ungulates and in contrast to the folivorous or insectivorous diets of extant xenarthrans. The ancestral reconstruction of the MMR values indicated a lack of a common pattern for all xenarthrans, strongly supporting the occurrence of low metabolic rates in extant forms due to their particular dietary preferences and arboreal or fossorial habits. Our results highlight the importance of considering different evidence beyond the phylogenetic position of extinct taxa, especially when extinct forms are exceptionally different from their extant relatives. Future studies evaluating the energetic needs of giant extinct xenarthrans should not assume lower metabolic rates for these extinct animals based solely on their phylogenetic position and the observations on their extant relatives.

Many remarkable innovations have repeatedly occurred across vast evolutionary distances. When convergent traits emerge on the tree of life, they are sometimes driven by the same underlying gene families, while other times many different gene families are involved. Conversely, a gene family may be repeatedly recruited for a single trait or many different traits. To understand the general rules governing convergence at both genomic and phenotypic levels, we systematically tested associations between 56 binary metabolic traits and gene count in 14,710 gene families from 993 species of Saccharomycotina yeasts. Using a recently developed phylogenetic approach that reduces spurious correlations, we discovered that gene family expansion and contraction was significantly linked to trait gain and loss in 45/56 (80%) of traits. While 601/746 (81%) of significant gene families were associated with only one trait, we also identified several \'keystone\' gene families that were significantly associated with up to 13/56 (23%) of all traits. These results indicate that metabolic innovations in yeasts are governed by a narrow set of major genetic elements and mechanisms.

Bats are the only mammals capable of powered flight and have correspondingly specialized body plans, particularly in their limb morphology. The origin of bat flight is still not fully understood due to an uninformative fossil record but, from the perspective of a functional transition, it is widely hypothesized that bats evolved from gliding ancestors. Here, we test predictions of the gliding-to-flying hypothesis of the origin of bat flight by using phylogenetic comparative methods to model the evolution of forelimb and hindlimb traits on a dataset spanning four extinct bats and 231 extant mammals with diverse locomotor modes. Our results reveal that gliders exhibit adaptive trait optima (1) toward relatively elongate forelimbs that are intermediate between those of bats and non-gliding arborealists, and (2) toward relatively narrower but not longer hindlimbs that are intermediate between those of non-gliders and bats. We propose an adaptive landscape based on limb length and width optimal trends derived from our modeling analyses. Our results support a hypothetical evolutionary pathway wherein glider-like postcranial morphology precedes a bat-like morphology adapted to powered-flight, setting a foundation for future developmental, biomechanical, and evolutionary research to test this idea.

Identifying along which lineages shifts in diversification rates occur is a central goal of comparative phylogenetics; these shifts may coincide with key evolutionary events such as the development of novel morphological characters, the acquisition of adaptive traits, polyploidization or other structural genomic changes, or dispersal to a new habitat and subsequent increase in environmental niche space. However, while multiple methods now exist to estimate diversification rates and identify shifts using phylogenetic topologies, the appropriate use and accuracy of these methods are hotly debated. Here we test whether five Bayesian methods-Bayesian Analysis of Macroevolutionary Mixtures (BAMM), two implementations of the Lineage-Specific Birth-Death-Shift model (LSBDS and PESTO), the approximate Multi-Type Birth-Death model (MTBD; implemented in BEAST2), and the Cladogenetic Diversification Rate Shift model (ClaDS2)-produce comparable results. We apply each of these methods to a set of 65 empirical time-calibrated phylogenies and compare inferences of speciation rate, extinction rate, and net diversification rate. We find that the five methods often infer different speciation, extinction, and net-diversification rates. Consequently, these different estimates may lead to different interpretations of the macroevolutionary dynamics. The different estimates can be attributed to fundamental differences among the compared models. Therefore, the inference of shifts in diversification rates is strongly method dependent. We advise biologists to apply multiple methods to test the robustness of the conclusions or to carefully select the method based on the validity of the underlying model assumptions to their particular empirical system.

OBJECTIVE: Under pollinator limitations, specialized pollination syndromes may evolve toward contrasting responses: a generalized syndrome with increased pollinator attraction, pollinator reward, and pollen transfer capacity; or the selfing syndrome with increased self-pollen deposition, but reduced pollinator attraction and pollen transfer capacity. The buzz-pollination syndrome is specialized to explore female vibrating bees as pollinators. However, vibrating bees become less-active pollinators at montane areas of the Atlantic Forest (AF) domain. This study investigated whether the specialized buzz-pollination syndrome would evolve toward an alternative floral syndrome in montane areas of the AF domain, considering a generalized and the selfing syndromes as alternative responses.
METHODS: We utilized a lineage within the buzz-pollinated Miconia as study system, contrasting floral traits between montane AF-endemic and non-endemic species. We measured and validated floral traits that were proxies for pollinator attraction, reward access, pollen transfer capacity, and self-pollen deposition. We inferred the evolution of floral trait via phylogenetic comparative methods.
RESULTS: AF-endemic species have selectively evolved greater reward access and more frequently had generalist pollination. Nonetheless, AF-endemic species also have selectively evolved toward lower pollen transfer capacity and greater self pollination. These patterns indicated a complex evolutionary process that has jointly favored a generalized and the selfing syndromes.
CONCLUSIONS: The buzz pollination syndrome can undergo an evolutionary disruption in montane areas of the AF domain. This floral syndrome is likely more labile than often assumed, allowing buzz-pollinated plants to reproduce in environments where vibrating bees are less-reliable pollinators.

Arboreality has evolved in all major vertebrate lineages and is often associated with morphological adaptations and increased diversification concomitant with accessing novel niche space. In squamate reptiles, foot, claw, and tail morphology are well-studied adaptations shown to be associated with transitions to arboreality. Here, we examined a less well understood trait-the keeled scale-in relation to microhabitat, climate, and diversification dynamics across a diverse lizard radiation, Agamidae. We found that the ancestral agamid had keeled dorsal but not ventral scales; further, dorsal and ventral keels are evolutionarily decoupled. Ventral keeled scales evolved repeatedly in association with arboreality and may be advantageous in reducing wear or by promoting interlocking when climbing. We did not find an association between keeled scales and diversification, suggesting keels do not allow finer-scale microhabitat partitioning observed in other arboreal-associated traits. We additionally found a relationship between keeled ventral scales and precipitation in terrestrial species where we posit that the keels may function to reduce scale degradation. Our results suggest that keeled ventral scales facilitated transitions to arboreality across agamid lizards, and highlight a need for future studies that explore their biomechanical function in relation to microhabitat and climate.