Biotic and abiotic factors driving the diversification dynamics of Crocodylia

Species diversity patterns are governed by complex interactions among biotic and abiotic factors over time and space, but are essentially the result of the diversification dynamics (differential speciation and extinction rates) over the long-term evolutionary history of a clade. Previous studies have suggested that temporal variation in global temperature drove long-term diversity changes in Crocodylia, a monophyletic group of large ectothermic organisms. We use a large database of crocodylian fossil occurrences (192 spp.) and body mass estimations, under a taxic approach, to characterize the global diversification dynamics of crocodylians since the Cretaceous, and their correlation with multiple biotic and abiotic factors in a Bayesian framework. The diversification dynamic of crocodylians, which appears to have originated in the Turonian (c. 92.5 Ma), is characterized by several phases with high extinction and speciation rates within a predominantly low long-term mean rate. Our results reveal long-term diversification dynamics of Crocodylia to be a highly complex process driven by a combination of biotic and abiotic factors which influenced the speciation and extinction rates in dissimilar ways. Higher crocodylian extinction rates are related to low body mass disparity, indicating selective extinctions of taxa at both ends of the body mass spectrum. Speciation rate slowdowns are noted when the diversity of the clade is high and the warm temperate climatic belt is reduced. Our finding supports the idea that temporal variations of body mass disparity, self-diversity, and the warm climate belt size provided more direct mechanistic explanations for crocodylian diversification than do proxies of global temperature.     

Internal aeration and respiration of submerged tomato hypocotyls are enhanced by ethylene-mediated aerenchyma formation and hypertrophy

With the impending threat that climate change is imposing on all terrestrial ecosystems, the ability of plants to adjust to changing environments is, more than ever, a very desirable trait. Tomato (Solanum lycopersicum L.) plants display a number of responses that allow them to survive under different abiotic stresses such as flooding. We focused on understanding the mechanism that facilitates oxygen diffusion to submerged tissues and the impact it has on sustaining respiration levels. We observed that, as flooding stress progresses, stems increase their diameter and internal porosity. Ethylene triggers stem hypertrophy by inducing cell wall loosening genes, and aerenchyma formation seems to involve programmed cell death mediated by hydrogen peroxide. We finally assessed whether these changes in stem morphology and anatomy are indeed effective to restore oxygen levels in submerged organs. We found that aerenchyma formation and hypertrophy not only increase oxygen diffusion toward the base of the plant, but also result in an augmented respiration rate. We consider that this response is crucial to maintain adventitious root development under such conditions and, therefore, making it possible for the plant to survive when the original roots die.     

A new Hemigrammus from the upper Río Vaupés,Colombia (Characiformes: Characidae), with a discussion on the presence of an enlarged urogenital papilla in the family

Hemigrammus xaveriellus sp. nov. is described from the upper Río Vaupés basin (Amazon basin), Departamento Guaviare, Colombia. It is distinguished from all congeners by the combination of the following characters: presence of a conspicuous, dark, longitudinal midlateral stripe extending along the body; presence of a conspicuous rounded, horizontally elongated humeral blotch anterior to the beginning of the dark midlateral stripe; seven scale rows between the dorsal fin and lateral line (vs. five to six); and five scale rows between the lateral line and pelvic-fin insertion (vs. three to four). The single mature male of He. xaveriellus possessed a well-developed urogenital papilla, an unusual feature among characids. The presence of an enlarged urogenital papilla in the family is discussed, and comments regarding the putative relationships of the new species are presented.     

Fish biodiversity of Saint Peter and Saint Paulʼs Archipelago,Mid-Atlantic Ridge,Brazil: new records and a species database

Saint Peter and Saint Paul's Archipelago (SPSPA), one of the smallest and most isolated island groups in the world, is situated on the Mid-Atlantic Ridge, between Brazil and the African continent. SPSPA has low species richness and high endemism; nonetheless, the diversity of fishes from deep habitats (>30 m depth) had not been previously studied in detail. Several expeditions conducted between 2009 and 2018 explored the shallow and deep reefs of SPSPA using scuba, closed-circuit rebreathers, manned submersibles, baited remote underwater stereo-videos (stereo-BRUV) and fishing between 0 and 1050 m depth. These expeditions yielded 41 new records of fishes for SPSPA: 9 in open waters, 9 in shallow waters (0–30 m), 8 in mesophotic ecosystems (30–150 m) and 15 in deeper reefs (>150 m). Combined with literature records of adult pelagic, shallow and deep-reef species, as well as larvae, the database of the fish biodiversity for SPSPA currently comprises 225 species (169 recorded as adult fishes and 79 as larvae, with 23 species found in both stages). Most of them (112) are pelagic, 86 are reef-associated species and 27 are deep-water specialists. Species accumulation curves show that the number of fish species has not yet reached an asymptote. Whereas the number of species recorded in SPSPA is similar to that in other oceanic islands in the Atlantic Ocean, the proportion of shorefishes is relatively lower, and the endemism level is the third highest in the Atlantic. Twenty-nine species are listed as threatened with extinction. Observations confirm the paucity of top predators on shallow rocky reefs of the island, despite the presence of several pelagic shark species around SPSPA. Because all of the endemic species are reef associated, it is argued that the new marine-protected areas created by the Brazilian government do not ensure the protection and recovery of SPSPA's biodiversity because they allow exploitation of the most vulnerable species around the archipelago itself. This study suggests a ban on reef fish exploitation inside an area delimited by the 1000 m isobath around the islands (where all known endemics are concentrated) as the main conservation strategy to be included in the SPSPA management plan being prepared by the Brazilian government.     

A molecular assessment of species diversity in Tympanopleura and Ageneiosus catfishes (Auchenipteridae: Siluriformes)

In order to test the congruence of genetic data to the morphologically defined Neotropical catfish genera Tympanopleura and Ageneiosus and explore species diversity, we generated 17 DNA barcodes from five of six species of Tympanopleura and 12 of 13 species of Ageneiosus. To discriminate limits between species, an automatic barcode gap discovery (ABGD), a generalised mixed yule-coalescent model (GYMC) and fixed distance thresholds Kimura two-parameter (K2P; 3%) were used to discriminate putative species limits from the DNA barcodes. The ABGD, GMYC and K2P methods agreed by each generating 13 clusters: six in Tympanopleura (five nominal plus one undescribed species) and seven in Ageneiosus. These clusters corresponded broadly to the described species, except in the case of the Ageneiosus ucayalensis group (A. akamai, A. dentatus, A. intrusus, A. ucayalensis, A. uranophthalmus and A. vittatus). Haplotype sharing and low divergences may have prevented molecular methods from distinguishing these species. We hypothesise that this is the result of a recent radiation of a sympatric species group distributed throughout the Amazon Basin. One putative new species of Tympanopleura was also supported by the molecular data. These results taken together highlight the utility of molecular methods such as DNA barcoding in understanding patterns of diversification across large geographic areas and in recognising overlooked diversity.     

Diet and Prey Selection of Dholes in Evergreen and Deciduous Forests of Southeast Asia

Endangered dholes (Cuon alpinus) are restricted to small and declining populations in Southeast Asia, and little is known about how their ecology differs within the region. We used DNA-confirmed scats and prey surveys to determine the seasonal diet and prey selection of dholes in 2 different landscapes that dominate Southeast Asia: closed evergreen forests in hilly terrain in northern Laos, and open deciduous forests in relatively flat terrain in eastern Cambodia. On both sites, muntjac (Muntiacus spp.; 20–28 kg) was the dominant prey item and was selectively consumed over other ungulates in all seasons. Our findings differ from previous conclusions, based largely on studies from India, that the preferred prey weight range of dholes was either 40–60 kg or 130–190 kg. Other important prey were sambar (Rusa unicolor) in Laos, and wild pig (Sus scrofa) and banteng (Bos javanicus) in Cambodia. Seasonal differences in overall diet occurred in Laos, but not Cambodia, primarily because of an increase in livestock consumption. The mean number of dhole scats in group defecation sites was higher in Cambodia (5.9 ± 0.5 [SE]) than Laos (2.4 ± 0.2), suggesting pack sizes were larger in Cambodia. Our results suggest that regardless of land cover type, prey diversity, or pack size, the management of muntjac will be important for conserving dhole populations in Southeast Asia. In Laos, we recommend that local villagers remove livestock from the protected area during the hot-dry season to reduce livestock predation by dholes. © 2020 The Authors. The Journal of Wildlife Management published by Wiley Periodicals LLC on behalf of The Wildlife Society.     

Two new endemic species of Ophiorrhiza L. (Rubiaceae: Ophiorrhizeae) from Davao Oriental,Philippines

Two new species of Ophiorrhiza collected from Mt Hamiguitan Range Wildlife Sanctuary in Davao Oriental, Philippines, are herein described and illustrated. Ophiorrhiza erythropilosa is the third Philippine species possessing involucral bracts and is further characterized by its predominantly villose stems that appear red due to strikingly red-violet trichomes, subpersistent bifid stipules, linear involucral bracts without prominent midrib, and 4 mm long urceolate corolla that is villose outside and lightly puberulous inside. Ophiorrhiza hamiguitanensis is characterized by its coriaceous, lanceolate leaves with attenuate apex and base, brochidodromous venation, subpersistent bilobed stipules with slightly recurved acute tips, presence of 1.5–2.5 mm long linear ensiform bracts, heterostylous flowers, clavate calyces and broadly obcordate capsules.