Drought Coincided with, but Does Not Explain, Late Holocene Megafauna Extinctions in SW Madagascar

Climate drying could have transformed ecosystems in southern Madagascar during recent millennia by contributing to the extinction of endemic megafauna. However, the extent of regional aridification during the past 2000 years is poorly known, as are the responses of endemic animals and economically important livestock to drying. We inferred ~1600 years of climate change around Lake Ranobe, SW Madagascar, using oxygen isotope analyses of monospecific freshwater ostracods (Bradleystrandesia cf. fuscata) and elemental analyses of lake core sediment. We inferred past changes in habitat and diet of introduced and extinct endemic megaherbivores using bone collagen stable isotope and 14C datasets (n = 63). Extinct pygmy hippos and multiple giant lemur species disappeared from the vicinity of Ranobe during a dry interval ~1000–700 cal yr BP, but the simultaneous appearance of introduced cattle, high charcoal concentrations, and other evidence of human activity confound inference of drought-driven extirpations. Unlike the endemic megafauna, relatively low collagen stable nitrogen isotope values among cattle suggest they survived dry intervals by exploiting patches of wet habitat. Although megafaunal extirpations coincided with drought in SW Madagascar, coupled data from bone and lake sediments do not support the hypothesis that extinct megafauna populations collapsed solely because of drought. Given that the reliance of livestock on mesic patches will become more important in the face of projected climate drying, we argue that sustainable conservation of spiny forests in SW Madagascar should support local livelihoods by ensuring that zebu have access to mesic habitat. Additionally, the current interactions between pastoralism and riparian habitats should be studied to help conserve the island’s biodiversity.

Discovery of a colossal slickhead (Alepocephaliformes: Alepocephalidae): an active-swimming top predator in the deep waters of Suruga Bay, Japan

A novel species of the family Alepocephalidae (slickheads), Narcetes shonanmaruae, is described based on four specimens collected at depths greater than 2171 m in Suruga Bay, Japan. Compared to other alepocephalids, this species is colossal (reaching ca. 140 cm in total length and 25 kg in body weight) and possesses a unique combination of morphological characters comprising anal fin entirely behind the dorsal fin, multiserial teeth on jaws, more scale rows than congeners, precaudal vertebrae less than 30, seven branchiostegal rays, two epurals, and head smaller than those of relatives. Mitogenomic analyses also support the novelty of this large deep-sea slickhead. Although most slickheads are benthopelagic or mesopelagic feeders of gelatinous zooplankton, behavioural observations and dietary analyses indicate that the new species is piscivorous. In addition, a stable nitrogen isotope analysis of specific amino acids showed that N. shonanmaruae occupies one of the highest trophic positions reported from marine environments to date. Video footage recorded using a baited camera deployed at a depth of 2572 m in Suruga Bay revealed the active swimming behaviour of this slickhead. The scavenging ability and broad gape of N. shonanmaruae might be correlated with its colossal body size and relatively high trophic position.

Consumption of soil nitrogen by plants in the use of fertilizer, green manure and biopreparation (study with 15n)

In a model experiment on a sod-podzolic medium loamy soil enriched with a stable nitrogen isotope 15N, the use of soil nitrogen by spring wheat studied when ammonium nitrate was introduced, mustard biomass and seed inoculation with the associated nitrogen fixer Rhizoagrin were introduced. It has been established that plants consume nitrogen primarily from recently applied nitrogen of fertilizer. When making biomass of mustard and inoculating seeds with Rhizoagrin, spring wheat uses soil nitrogen, with the integrated use of these components and applying ammonium nitrate soil nitrogen and fertilizer. The accumulation of plant biomass predominantly increases from recently applied nitrogen of fertilizer, both separately and when combined with green manure and seed inoculation with a biopreparation and is 14-28% relative to the control without fertilizers. When applying nitrogen fertilizer, as well as when combined with green manure and biopreparation, the concentration of nitrogen in spring wheat increases up to 1.5 times. There is a clear upward trend in the concentration of nitrogen in plants with the addition of mustard biomass and it increases with inoculation of seeds with Rhizoagrin. As a result, the accumulation of total nitrogen in plants increases when nitrogen fertilizer is applied, and the use of mustard biomass and biopreparation increases this indicator by 1.2 times, which is due to the presence of nitrogen compounds available to plants in the nutrient medium. The accumulation in plants of 15N characterizes the consumption of soil nitrogen by plants, when introducing nitrogen fertilizer, this indicator is less, and using only biomass of mustard and Rhizoagrin is equivalent to control without fertilizers, indicating large amounts of mineralized nitrogen consumption from the soil when using the last two components, and that nitrogen fertilizer is not a factor in the mineralization of soil organic matter. The use of mustard biomass for spring wheat and seed inoculation with Rhizoagrin leads to the consumption of soil nitrogen by plants during the initial growing season.