Niche evolution and phylogenetic community paleoecology of Late Ordovician crinoids

Fossil crinoids are exceptionally suited to deep-time studies of community paleoecology and niche partitioning. By merging ecomorphological trait and phylogenetic data, this study summarizes niche occupation and community paleoecology of crinoids from the Bromide fauna of Oklahoma (Sandbian, Upper Ordovician). Further, patterns of community structure and niche evolution are evaluated over a ~5 million-year period through comparison with the Brechin Lagerstätte (Katian, Upper Ordovician). We establish filtration fan density, food size selectivity, and body size as major axes defining niche differentiation, and niche occupation is strongly controlled by phylogeny. Ecological strategies (i.e., adaptive zones) were relatively static over the study interval at high taxonomic scales, but niche differentiation and specialization increased in most subclades. Changes in disparity and species richness indicate the transition between the early-middle Paleozoic Crinoid Evolutionary Faunas was already underway by the Katian due to ecological drivers and was not triggered by the Late Ordovician mass extinction.

Failure to Find Altruistic Food Sharing in Rats

Prior research has found that one rat will release a second rat from a restraint in the presence of food, thereby allowing that second rat access to food. Such behavior, clearly beneficial to the second rat and costly to the first, has been interpreted as altruistic. Because clear demonstrations of altruism in rats are rare, such findings deserve a careful look. The present study aimed to replicate this finding, but with more systematic methods to examine whether, and under what conditions, a rat might share food with its cagemate partner. Rats were given repeated choices between high-valued food (sucrose pellets) and 30-s social access to a familiar rat, with the (a) food size (number of food pellets per response), and (b) food motivation (extra-session access to food) varied across conditions. Rats responded consistently for both food and social interaction, but at different levels and with different sensitivity to the food-access manipulations. Food production and consumption was high when food motivation was also high (food restriction) but substantially lower when food motivation was low (unlimited food access). Social release occurred at moderate levels, unaffected by the food-based manipulations. When food was abundant and food motivation low, the rats chose food and social options about equally often, but sharing (food left unconsumed prior to social release) occurred at low levels across sessions and conditions. Even under conditions of low food motivation, sharing occurred on only 1% of the sharing opportunities. The results are therefore inconsistent with claims in the literature that rats are altruistically motivated to share food with other rats.

Effect of environment on functional traits of co-occurring water beetles

We investigated trait-environment relationships of co-occurring aquatic Coleoptera specifically true water beetles in anthropogenic ponds from the Western Ghats, India for the first time. Our objectives were to: (1) identify species assemblages; (2) study species traits; (3) study trait-environment relationships of co-occurring species. We analysed 132 samples collected using standardised quantitative method during the years 2016 and 2017. We found 16 significant assemblages using Fager's index, where most of the pairs have body size ratio of 1.3 or more. For example, Laccophilus parvulus and Hydaticus satoi pair has body size ratio of 3.98, and both are predators, indicating that body size is a function of food size. Moreover, factor analysis revealed three major swimming categories of studied beetles, namely fast swimmers, maneuverers and poor swimmers. Further, the RLQ analysis, and combined approach of RLQ and fourth-corner analysis showed that environmental variables affected species traits. For instance, odonate nymphs and submerged vegetation were positively associated with fast swimmers like Laccophilus inefficiens and Hydaticus satoi. The assemblage of congeners Hydroglyphus inconstans and H. flammulatus can be predator-mediated as these beetles showed negative association with odonate nymphs as well as competitive to obtain resource by showing positive association with chironomid larvae. Therefore, the traits studied were important for ecological performances of species in ponds. This study has also highlighted the importance of anthropogenic ponds in the Western Ghats as biodiversity refuges of ecologically unique and evolutionary old major extant lineages of water beetles.

Failure to Find Altruistic Food Sharing in Rats

Prior research has found that one rat will release a second rat from restraint in the presence of food, thereby allowing that second rat access to food. Such behavior, clearly beneficial to the second rat and costly to the first, has been interpreted as altruistic. Because clear demonstrations of altruism in rats are rare, such findings deserve a careful look. The present study aimed to replicate this finding, but with more systematic methods to examine whether, and under what conditions, a rat might share food with its cagemate partner. Rats were given repeated choices between high-valued food (sucrose pellets) and 30-s social access to a familiar rat, with the (a) food size (number of food pellets per response), and (b) food motivation (extra-session access to food) varied across conditions. Rats responded consistently for both food and social interaction, but at different levels and with different sensitivity to the food-access manipulations. Food production and consumption was high when food motivation was also high (food restriction) but substantially lower when food motivation was low (unlimited food access). Social release occurred at moderate levels, unaffected by the food-based manipulations. When food was abundant and food motivation low, the rats chose food and social options about equally often, but sharing (food left unconsumed prior to social release) occurred at low levels across sessions and conditions. Even under conditions of low food motivation, sharing occurred on only 1% of the sharing opportunities. The results are therefore inconsistent with claims in the literature that rats are altruistically motivated to share food with other rats.

Hierarchical controls on extinction selectivity across the diplobathrid crinoid phylogeny

Identifying correlates of extinction risk is important for understanding the underlying mechanisms driving differential rates of extinction and variability in the temporal durations of taxa. Increasingly, it is recognized that the effects of multiple, potentially interacting variables and phylogenetic relationships should be incorporated when studying extinction selectivity to account for covariation of traits and shared evolutionary history. Here, I explore a variety of biological and ecological controls on genus longevity in the global fossil record of diplobathrid crinoids by analyzing the combined effects of species richness, habitat preference, body size, filtration fan density, and food size selectivity. I employ a suite of taxic and phylogenetic approaches to (1) quantitatively compare and rank the relative effects of multiple factors on taxonomic longevity and (2) determine how phylogenetic comparative approaches alter interpretations of extinction selectivity. I find controls on diplobathrid genus duration are hierarchically structured, where species richness is the primary predictor of duration, habitat is the secondary predictor, and combinations of ecological and biological traits are tertiary controls. Ecology plays an important but complex role in the generation of crinoid macroevolutionary patterns. Notably, tolerance of environmental heterogeneity promotes increased genus duration across diplobathrid crinoids, and the effects of traits related to feeding ecology vary depending on habitat lithology. Finally, I find accounting for phylogeny does not consistently decrease the significance of correlations between traits and genus duration, as is commonly expected. Instead, the strength of relationships between traits and duration may increase, decrease, or remain statistically similar, and both the magnitude and direction of these shifts are generally unpredictable. However, traits with strong correlations and/or moderately large effect sizes (Cohen's f2 > 0.15) under taxic approaches tend to remain qualitatively unchanged under phylogenetic approaches.

Influence of Different Algal Diets on Larval Growth Rates in the Marine Serpulidae Polychaete Worm Spirobranchus kraussii

Effects of food availability on larval growth and survival of Spirobranchus kraussii were studied by feeding larvae different algal diets. Newly hatched larvae of S. kraussii were fed four different marine microalgae species, singly and in various mixtures. The best growth was observed when fed C. vulgaris, N. oculata as a single species and mixed-algal diet during day 15 after fertilization. Mortality was low for larvae (max. 5%); survival rate more than 95%. These results suggest that S. kraussii larvae have the capacity to feed using alternative sources of energy, and food size and quality can affect their growth and sustainability.