40 new specimens of Ichthyornis provide unprecedented insight into the postcranial morphology of crownward stem group birds.

Ichthyornis has long been recognized as a pivotally important fossil taxon for understanding the latest stages of the dinosaur-bird transition, but little significant new postcranial material has been brought to light since initial descriptions of partial skeletons in the 19th Century. Here, we present new information on the postcranial morphology of Ichthyornis from 40 previously undescribed specimens, providing the most detailed morphological assessment of Ichthyornis to date. The new material includes four partially complete skeletons and numerous well-preserved isolated elements, enabling new anatomical observations such as muscle attachments previously undescribed for Mesozoic euornitheans. Among the elements that were previously unknown or poorly represented for Ichthyornis, the new specimens include an almost-complete axial series, a hypocleideum-bearing furcula, radial carpal bones, fibulae, a complete tarsometatarsus bearing a rudimentary hypotarsus, and one of the first-known nearly complete three-dimensional sterna from a Mesozoic avialan. Several pedal phalanges are preserved, revealing a remarkably enlarged pes presumably related to foot-propelled swimming. Although diagnosable as Ichthyornis, the new specimens exhibit a substantial degree of morphological variation, some of which may relate to ontogenetic changes. Phylogenetic analyses incorporating our new data and employing alternative morphological datasets recover Ichthyornis stemward of Hesperornithes and Iaceornis, in line with some recent hypotheses regarding the topology of the crownward-most portion of the avian stem group, and we establish phylogenetically-defined clade names for relevant avialan subclades to help facilitate consistent discourse in future work. The new information provided by these specimens improves our understanding of morphological evolution among the crownward-most non-neornithine avialans immediately preceding the origin of crown group birds.

A new species of the genus Colopalpus Pritchard and Baker (Trombidiformes: Tenuipalpidae) from China, with ontogenetic patterns in chaetotaxy

A new species, Colopalpus hibiscus sp. nov. (Acari: Tenuipalpidae) is described from Hibiscus in Hainan province, China. The ontogenetic changes in the idiosoma and leg chaetotaxy on adults (female and male) and immature stages of this new species are presented. A key to species of Colopalpus is also provided.

Ecology of New Zealand Deep-sea Chondrichthyans

<p>Deep-sea chondrichthyans represent nearly half of the known species of sharks, rays, and chimaeras. Most are poorly known, largely due to their historically low economic value, and thus, low prioritization for research efforts and targeted sampling. Globally, many deep-sea fisheries have proven to be unsustainable, as deep-sea species are generally characterised with life history traits, resulting in low biological productivity. Although generally not targeted, there is a lack of data on New Zealand deep-sea chondrichthyans, despite regularly occurring as bycatch, with no mitigation in place to limit catches. This thesis described aspects of life histories for data deficient deep-sea chondrichthyans caught as bycatch in New Zealand deep-sea fisheries. In Chapter II, research trawl survey data were used to describe and evaluate length-weight relationships, which were found to greatly differ from parameters reported by FishBase. This was followed by the application of a set of models to detect changes in weight at length relationships, and assess if these changes correspond to biological or ecological events, such as length-at-maturity or ontogenetic changes in diet. Chapter III evaluates deep-sea chondrichthyan aggregations and social associations. Not all species were found to engage in aggregative behaviour, but those that did suggested patterns of sex- and size-specific associations which varied with catch density. Adult females were caught most frequently in low densities and were highly associated with other adult females, adult males consistently highly associated with each other, and the highest density catches were dominated by juvenile individuals. These trends may be driven by factors such as foraging, predator avoidance or sexual conflict avoidance. Chapters IV, V, and VI examine, respectively, details of the reproduction, life history, and diet of prickly dogfish (Oxynotus bruniensis), longnose spookfish (Harriotta raleighana) and Pacific spookfish (Rhinochimaera pacifica), and brown chimaera (Chimaera carophila) and black ghost shark (Hydrolagus homonycteris). All species were found to have life histories characteristic of low productivity, including reaching maturation at a large proportion of their maximum length, and having low fecundity. Additional novel biological results included: DNA identification of prey revealed that O. bruniensis preyed exclusively on the egg capsules of holocephalans, potentially making it the only known elasmobranch with a diet reliant solely upon other chondrichthyans; sperm storage was confirmed in female H. raleighana, R. pacifica, and C. carophila; and sexual dimorphism in snout length was found in H. raleighana, where male relative snout size increased at sexual maturity, suggesting that the snout is a secondary sexual characteristic. The depth range of most New Zealand deep-sea chondrichthyans may provide some refuge from current fishing activity. However, results from this thesis have suggested that the species examined here have life histories characteristic of low productivity, and engage in behaviours that will have implications for selective mortality by spatially or temporally stratified fishing. Oxynotus bruniensis, in particular, is likely at higher risk from the impact of fishing than currently estimated, given its reproductive characteristics, highly specialised diet, and distribution overlap with deep-sea fisheries. Continued monitoring and a greater collection of biological data from additional and alternative sources (e.g. fisheries observer program, local fishers, underwater vehicles and video) is recommended to fully understand and negate mortality from human activities.</p>

Ecology of New Zealand Deep-sea Chondrichthyans

<p>Deep-sea chondrichthyans represent nearly half of the known species of sharks, rays, and chimaeras. Most are poorly known, largely due to their historically low economic value, and thus, low prioritization for research efforts and targeted sampling. Globally, many deep-sea fisheries have proven to be unsustainable, as deep-sea species are generally characterised with life history traits, resulting in low biological productivity. Although generally not targeted, there is a lack of data on New Zealand deep-sea chondrichthyans, despite regularly occurring as bycatch, with no mitigation in place to limit catches. This thesis described aspects of life histories for data deficient deep-sea chondrichthyans caught as bycatch in New Zealand deep-sea fisheries. In Chapter II, research trawl survey data were used to describe and evaluate length-weight relationships, which were found to greatly differ from parameters reported by FishBase. This was followed by the application of a set of models to detect changes in weight at length relationships, and assess if these changes correspond to biological or ecological events, such as length-at-maturity or ontogenetic changes in diet. Chapter III evaluates deep-sea chondrichthyan aggregations and social associations. Not all species were found to engage in aggregative behaviour, but those that did suggested patterns of sex- and size-specific associations which varied with catch density. Adult females were caught most frequently in low densities and were highly associated with other adult females, adult males consistently highly associated with each other, and the highest density catches were dominated by juvenile individuals. These trends may be driven by factors such as foraging, predator avoidance or sexual conflict avoidance. Chapters IV, V, and VI examine, respectively, details of the reproduction, life history, and diet of prickly dogfish (Oxynotus bruniensis), longnose spookfish (Harriotta raleighana) and Pacific spookfish (Rhinochimaera pacifica), and brown chimaera (Chimaera carophila) and black ghost shark (Hydrolagus homonycteris). All species were found to have life histories characteristic of low productivity, including reaching maturation at a large proportion of their maximum length, and having low fecundity. Additional novel biological results included: DNA identification of prey revealed that O. bruniensis preyed exclusively on the egg capsules of holocephalans, potentially making it the only known elasmobranch with a diet reliant solely upon other chondrichthyans; sperm storage was confirmed in female H. raleighana, R. pacifica, and C. carophila; and sexual dimorphism in snout length was found in H. raleighana, where male relative snout size increased at sexual maturity, suggesting that the snout is a secondary sexual characteristic. The depth range of most New Zealand deep-sea chondrichthyans may provide some refuge from current fishing activity. However, results from this thesis have suggested that the species examined here have life histories characteristic of low productivity, and engage in behaviours that will have implications for selective mortality by spatially or temporally stratified fishing. Oxynotus bruniensis, in particular, is likely at higher risk from the impact of fishing than currently estimated, given its reproductive characteristics, highly specialised diet, and distribution overlap with deep-sea fisheries. Continued monitoring and a greater collection of biological data from additional and alternative sources (e.g. fisheries observer program, local fishers, underwater vehicles and video) is recommended to fully understand and negate mortality from human activities.</p>

Macroevolutionary Changes of Plants on Islands

<p>Insularity is known to produce predictable evolutionary changes in plants. For example, herbaceous plants often evolve woodiness and seeds tend to have reduced dispersal capabilities on islands. However, our understanding of how other plant traits may evolve on islands is lacking. Furthermore, plants are modular organisms and by investigating evolutionary changes in specific plant traits we may better understand macroevolutionary processes on islands. In this thesis, I investigate evolutionary changes in a range of plant traits on islands. First, I tested for evolutionary changes in seed size on islands (Chapter 2). Island plants consistently produced larger seeds than mainland relatives. Furthermore, this result was consistent regardless of differences in dispersal mode, growth form and evolutionary history. Selection may favour increased seed size to reduce dispersal distances. Additionally, selection may favour larger seeds due to the competitive advantage conferred to developing seedlings. Many animal taxa exhibit increased sexual size dimorphism (SSD) on islands, as predicted by the niche variation hypothesis. However, patterns of SSD among dioecious plants on islands are unknown. In Chapter 3 I tested for differences in SSD of dioecious plants that colonized four island groups from New Zealand (mainland). The degree of SSD did not vary predictable between island and mainland plants, contrary to predictions of the niche variation hypothesis. However, SSD was consistently female biased on the mainland and results suggest selection is acting to increase the size of both sexes on islands. Evolutionary changes in island plants may be a response to herbivory by unique large browsers. For example, the divaricate growth form is common in the New Zealand flora and may have deterred browsing moa. In Chapter 4 I tested for differences in traits associated with the divaricate growth form between plants from mainland New Zealand and Chatham Island. Results suggest that an absence of moa on Chatham Island has relaxed selection for traits associated with the divaricate growth form. An emerging body of research suggests aposematism (warning signals to herbivores) may be common in plants. However, previous investigations have not appreciated the fact that the perspective of terrestrial herbivores changes as plants grown vertically. Furthermore, ontogenetic changes in the capacity of plants to defend themselves may influence the reliability of warning signals. In Chapter 5 I tested for ontogenetic changes in two potentially aposematic signals produced by Pseudopanax crassifolius. Aposematism on upper leaf surfaces peaked early in ontogeny, providing a dishonest signal of defense. Conversely, signaling on the underside of leaves peaked later in ontogeny and scaled positively with structural defenses. The results of this thesis suggest selection is acting on specific plant traits on islands. Evolutionary pathways, such as the evolution of woodiness, may be better explained by considering selection acting on other plant traits. For example, selection acting on seed size may facilitate evolutionary size changes evident at later life-history stages. A lack of consensus exists regarding the role of insular herbivores in the evolution of island plants. The results of Chapters 4 and 5 suggest herbivory has played an important role in the evolution of novel morphology of island plants. Considering trait specific changes of plants on islands may further our understanding of prominent evolutionary pathways by pinpointing the action of selection.</p>

Ontogenetic changes in limb posture, kinematics, forces, and joint moments in American alligators (Alligator mississippiensis)

As animals increase in size, common patterns of morphological and physiological scaling may require them to perform behaviors such as locomotion while experiencing a reduced capacity to generate muscle force and an increased risk of tissue failure. Large mammals are known to manage increased mechanical demands by using more upright limb posture. However, the presence of such size-dependent changes in limb posture has rarely been tested in animals that use non-parasagittal limb kinematics. Here, we used juvenile to subadult American alligators (total length 0.46–1.27 m, body mass 0.3–5.6 kg) and examined their limb kinematics, forces, joint moments, and center of mass to test for ontogenetic shifts in posture and limb mechanics. Larger alligators typically walked with a more adducted humerus and femur and a more extended knee. Normalized peak joint moments reflected these postural patterns, with shoulder and hip moments imposed by the ground reaction force showing relatively greater magnitudes in the smallest individuals. Thus, as larger alligators use more upright posture, they incur relatively smaller joint moments than smaller alligators, which could reduce the forces that the shoulder and hip adductors of larger alligators must generate. The center of mass (CoM) shifted nonlinearly from juveniles through subadults. The more anteriorly positioned CoM in small alligators, together with their compliant hindlimbs, contributes to their higher forelimb and lower hindlimb normalized peak vertical forces in comparison to larger alligators. Future studies of alligators that approach maximal adult sizes could give further insight into how animals with non-parasagittal limb posture modulate locomotor patterns as they increase in mass and experience changes in the CoM.

Ontogeny in the steinmanellines (Bivalvia: Trigoniida): an intra- and interspecific appraisal using the Early Cretaceous faunas from the Neuquén Basin as a case study

Despite the paleontological relevance and paleobiological interest of trigoniid bivalves, our knowledge of their ontogeny—an aspect of crucial evolutionary importance—remains limited. Here, we assess the intra- and interspecific ontogenetic variations exhibited by the genus Steinmanella Crickmay (Myophorellidae: Steinmanellinae) during the early Valanginian–late Hauterivian of Argentina and explore some of their implications. The (ontogenetic) allometric trajectories of seven species recognized for this interval were estimated from longitudinal data using 3D geometric morphometrics, segmented regressions, and model selection tools, and then compared using trajectory analysis and allometric spaces. Our results show that within-species shell shape variation describes biphasic ontogenetic trajectories, decoupled from ontogenetic changes shown by sculpture, with a gradual decay in magnitude as ontogeny progresses. The modes of change characterizing each phase (crescentic growth and anteroposterior elongation, respectively) are conserved across species, thus representing a feature of Steinmanella ontogeny; its evolutionary origin is inferred to be a consequence of the rate modification and allometric repatterning of the ancestral ontogeny. Among species, trajectories are more variable during early ontogenetic stages, becoming increasingly conservative at later stages. Trajectories’ general orientation allows recognition of two stratigraphically consecutive groups of species, hinting at a potentially higher genus-level diversity in the studied interval. In terms of functional morphology, juveniles had a morphology more suited for active burrowing than adults, whose features are associated with a sedentary lifestyle. The characteristic disparity of trigoniids could be related to the existence of an ontogenetic period of greater shell malleability betrayed by the presence of crescentic shape change.

Growing up in a new world: trait divergence between rural, urban, and invasive populations of an amphibian urban invader

Cities are focal points of introduction for invasive species. Urban evolution might facilitate the success of invasive species in recipient urban habitats. Here we test this hypothesis by rearing tadpoles of a successful amphibian urban coloniser and invader in a common garden environment. We compared growth rate, morphological traits, swimming performance, and developmental rate of guttural toad tadpoles (Sclerophrys gutturalis) from native rural, native urban, and non-native urban habitats. By measuring these traits across ontogeny, we were also able to compare divergence across different origins as the tadpoles develop. The tadpoles of non-native urban origin showed significantly slower developmental rate (e.g., the proportion of tadpoles reaching Gosner stage 31 or higher was lower at age 40 days) than tadpoles of native urban origin. Yet, tadpoles did not differ in growth rate or any morphological or performance trait examined, and none of these traits showed divergent ontogenetic changes between tadpoles of different origin. These findings suggest that prior adaptation to urban habitats in larval traits likely does not play an important role in facilitating the invasion success of guttural toads into other urban habitats. Instead, we suggest that evolutionary changes in larval traits after colonization (e.g., developmental rate), together with decoupling of other traits and phenotypic plasticity might explain how this species succeeded in colonising extra-limital urban habitats.

The effectiveness of eyespots and masquerade in protecting artificial prey across ontogenetic and seasonal shifts

When constraints on antipredator coloration shift over the course of development, it can be advantageous for animals to adopt different color strategies for each life stage. Many caterpillars in the genus Papilio exhibit unique ontogenetic color sequences: e.g., early instars that masquerade as bird feces, with later instars possessing eyespots. I hypothesize that larvae abandon feces masquerade in lieu of eyespots due to ontogenetic changes in signaler size. This ontogenetic pattern also occurs within broader seasonal shifts in background color and predator activity. I conducted predation experiments with artificial prey to determine how potential signaling constraints (specifically size and season) shape predation risk, and consequently the expression of ontogenetic color change in Papilio larvae. Seasonally, both predation and background greenness declined significantly from July to September, though there was little evidence that these patterns impacted the effectiveness of either color strategy. Caterpillar size and color strongly affected the attack rate of avian predators: attacks increased with prey size regardless of color, and eyespotted prey were attacked more than masquerading prey overall. These results may reflect a key size-mediated tradeoff between conspicuousness and intimidation in eyespotted prey, and raise questions about how interwoven aspects of behavior and signal environment might maintain the prevalence of large, eyespotted larvae in nature.