Ancient hybrid origin of the eastern wolf not yet off the table: a comment on Rutledge et al. (2015)

A recent study of North American canids by Rutledge et al. (Biol. Lett. 11, 20150303 (doi:10.1098/rsbl.2015.0303)) refutes the hypothesized hybrid origin of the eastern wolf (EW) based on genomic evidence against very recent hybridization. However, the analyses do not rule out the possibility of more ancient hybridization. Claims to have resolved the evolutionary origin of the EW are therefore inappropriate. Importantly, though, we plead that uncertainty about the ancient history of the taxon should not affect current conservation policy.     

乌尔吉晚更新世动物群和古生态环境

乌尔吉地区晚更新世地层出露广泛,哺乳动物化石常有发现.乌尔吉动物群属于猛犸象—披毛犀动物群,其时代为晚更新世晚期.动物群的生态性质明显反映了当时应为寒温带湿冷草原为主间有疏林和少量灌丛的自然景观.     

黑龙江西三江地区早白垩世孢粉组合

本文研究黑龙江东部西三江地区中生代煤系地层3个岩组中的孢粉组合。其中城子河组孢粉组合丰富,时代属欧特里期至巴列姆期,但目前材料尚不能对城子河组进行有意义的孢粉地层再分。穆棱组下部与城子河组的孢粉组合相似,反映植物群的渐变过程。东荣组的孢粉组合及其与邻区地层的对比关系亦有讨论,其时代有属凡兰吟期的可能。     

Post‐glacial patterns in vegetation dynamics in Romania: homogenization or differentiation?

Aim This paper examines eight fossil pollen datasets from Romania with the aim of exploring regional and elevational patterns in site similarity throughout the Holocene. In particular, we aim to determine whether there are clear intervals of homogenization/differentiation and to ascertain the potential driving factors. Location Romania. Methods Qualitative (pollen diagrams) and numerical methods including principal components analysis and Bray–Curtis similarity analyses were used. Results We found strong variability in the past vegetation dynamics during the Holocene. Bray–Curtis similarity analyses show large fluctuations in vegetation similarity and distinct periods of homogenization and differentiation throughout the Holocene. The magnitude and length of these periods appear quite variable in time, but the significant ones can be delimited as follows: (1) differentiation between 11,250 and 11,000 cal. yr bp , 10,000 and 9750 cal. yr bp , 6000 and 5750 cal. yr bp , 2500 and 2250 cal. yr bp , and especially over the last 200 years; and (2) homogenization between 9750 and 9500 cal. yr bp , and 2750 and 2500 cal. yr bp , with more stable periods between 9000 and 7750 cal. yr bp , 4750 and 3500 cal. yr bp , and 2000 and 1000 cal. yr bp . Main conclusions First, periods of biotic homogenization that occurred before significant anthropogenic impact on vegetation demonstrate that not all homogenization is a product of anthropogenic change: it can also be driven by natural causes. In fact, recent human impact (over the last 200 years) appears to have resulted in increased regional differentiation and not in homogenization – a result that contradicts most studies based on more modern, short‐term records. Second, both abiotic (climate and disturbance) and biotic factors are likely drivers of intervals of differentiation and homogenization. We suggest that differentiation may be triggered primarily by climate changes and disturbances (mostly natural pre‐2500 cal. yr bp and human‐induced thereafter), whereas homogenization may be driven predominantly by biotic interactions (e.g. immigration and interspecific competition). Third, this long‐term study raises awareness that assessments of pattern in vegetation homogenization/differentiation may depend on the specific time period and length of investigation. Long‐term investigations through multiple generations are likely to yield particularly useful information on the mechanisms and effects of biotic homogenization.     

Fine‐scale heterogeneity in beetle assemblages under co‐occurring Eucalyptus in the same subgenus

Aim Insect biodiversity is often positively associated with habitat heterogeneity. However, this relationship depends on spatial scale, with most studies focused on differences between habitats at large scales with a variety of forest tree species. We examined fine‐scale heterogeneity in ground‐dwelling beetle assemblages under co‐occurring trees in the same subgenus: Eucalyptus melliodora A. Cunn. ex Schauer and E. blakelyi Maiden (Myrtaceae). Location Critically endangered grassy woodland near Canberra, south‐eastern Australia. Methods We used pitfall traps and Tullgren funnels to sample ground‐dwelling beetles from the litter environment under 47 trees, and examined differences in diversity and composition at spatial scales ranging from 100 to 1000 m. Results Beetle assemblages under the two tree species had distinctive differences in diversity and composition. We found that E. melliodora supported a higher richness and abundance of beetles, but had higher compositional similarity among samples. In contrast, E. blakelyi had a lower abundance and species richness of beetles, but more variability in species composition among samples. Main conclusions Our study shows that heterogeneity in litter habitat under co‐occurring and closely related eucalypt species can influence beetle assemblages at spatial scales of just hundreds of metres. The differential contribution to fine‐scale alpha and beta diversity by each eucalypt can be exploited for conservation purposes by ensuring an appropriate mix of the two species in the temperate woodlands where they co‐occur. This would help not only to maximize biodiversity at landscape scales, but also to maintain heterogeneity in species richness, trophic function and biomass at fine spatial scales.     

Using ecological niche modelling to evaluate niche stability in deep time

Aim To investigate relative niche stability in species responses to various types of environmental pressure (biotic and abiotic) on geological time‐scales using the fossil record. Location The case study focuses on Late Ordovician articulate brachiopods of the Cincinnati Arch in eastern North America. Methods Species niches were modelled for a suite of fossil brachiopod species based on five environmental variables inferred from sedimentary parameters using GARP and Maxent . Niche stability was assessed by comparison of (1) the degree of overlap of species distribution models developed for a time‐slice and those generated by projecting niche models of the previous time‐slice onto environmental layers of a second time‐slice using GARP and Maxent , (2) Schoener’s D statistic, and (3) the similarity of the contribution of each environmental parameter within Maxent niche models between adjacent time‐slices. Results Late Ordovician brachiopod species conserved their niches with high fidelity during intervals of gradual environmental change but responded to inter‐basinal species invasions through niche evolution. Both native and invasive species exhibited similar levels of niche evolution in the invasion and post‐invasion intervals. Niche evolution was related mostly to decreased variance within the former ecological niche parameters rather than to shifts to new ecospace. Main conclusions Although the species examined exhibited morphological stasis during the study interval, high levels of niche conservatism were observed only during intervals of gradual environmental change. Rapid environmental change, notably inter‐basinal species invasions, resulted in high levels of niche evolution among the focal taxa. Both native and invasive species responded with similar levels of niche evolution during the invasion interval and subsequent environmental reorganization. The assumption of complete niche conservatism frequently employed in ecological niche modelling (ENM) analyses to forecast or hindcast species geographical distributions is more likely to be accurate for climate change studies than for invasive species analyses over geological time‐scales.     

Direct and Indirect Effects of Fire on Eastern Box Turtles

Prescribed fire is an increasingly important management tool for eastern deciduous forests, but relativity little is known about the direct effects of fire on the eastern box turtle (Terrapene carolina carolina). We used very high frequency (VHF) transmitters to monitor mortality, movement, and spatial ecology of 118 box turtles in response to 17 prescribed fires across 4 seasons and 3 sites in east Tennessee, USA, during 2016–2018. Annual survival of box turtles that experienced a prescribed fire event was lower (0.87 ± 0.04 [SE]) than turtles that did not (0.98 ± 0.01) and was negatively correlated with fire intensity, fire temperature the turtle experienced, and litter depth. All prescribed fire-related mortalities occurred during the early (Apr–May, n = 5) or late growing season (Sep–Oct, n = 1). Fourteen percent of box turtles we captured exhibited damage to their carapace from previous fire events. Box turtles that survived prescribed fires were in microsites that did not burn, moved to unburned areas during the fire, or burrowed following ignition. Home range size was similar before and after burns and sinuosity of movements did not differ in burned or unburned areas. Our results indicate that though box turtles are susceptible to prescribed fire during their active season, they have behavioral and physical traits that reduce the direct effects of prescribed fire. Prescribed fire practitioners should be aware of the risks of fire, particularly during the active season. We suggest managers consider altering prescribed fire intensity, seasonality, and firing pattern to minimize risk of direct effects where box turtles are of concern. © 2020 The Wildlife Society.     

Influence of drainage basin topography and elevation on carbon dioxide and methane supersaturation of stream water

The partial pressures of CO₂ (pCO₂) andCH₄ (pCH₄) in streams are not only governed byinstream processes, but also by transformations occurring in soil andgroundwater ecosystems. As such, stream water pCO₂ andpCH₄ can provide a tool to assess ecosystem respiration andanaerobic metabolism throughout drainage basins. We conducted three surveyssampling the gas content of streams in eastern Tennessee and western NorthCarolina to assess factors regulating ecosystem metabolism in catchmentswith contrasting geomorphologies, elevations and soil organic matterstorage. In our first survey, the influence of drainage basin geomorphologyon ecosystem respiration was examined by sampling streams drainingcatchments underlain by either shale or dolomite. Geomorphology isinfluenced by geology with shale catchments having shallower soils, broader,unconstrained valley floors compared with dolomite catchments.pCO₂ varied little between catchment types but increased froman average of 3340 ppmv in spring to 9927 ppmv in summer or 9.3 and 28 timesatmospheric equilibrium (pCO_2(equilib)), respectively. Incontrast, pCH₄ was over twice as high in streams drainingshale catchments (306 ppmv; pCH_4(equilib) = 116) compared withmore steeply incised dolomite basins (130 ppmv; pCH_4(equilib)= 51). Using the ratio of pCH₄:pCO₂ as an indexof anaerobic metabolism, shale catchments had nearly twice as muchanaerobiosis (pCH₄:pCO₂ = 0.046) than dolomitedrainages (pCH₄:pCO₂ = 0.024). In our secondsurvey, streams were sampled along an elevational gradient (525 to 1700 m)in the Great Smoky Mountains National Park, USA where soil organic matterstorage increases with elevation. pCO₂ did not vary betweenstreams but increased from 5340 ppmv (pCO_2(equilib) = 15) to8565 ppmv (pCO_2(equilib) = 24) from spring to summer,respectively. During spring pCH₄ was low and constant acrossstreams, but during summer increased with elevation ranging from 17 to 2068ppmv (pCH_4(equilib) = 10 to 1216). The contribution ofanaerobiosis to total respiration was constant during spring(pCH₄:pCO₂ = 0.017) but during summer increasedwith elevation from 0.002 at 524 m to 0.289 at 1286 m. In our last survey,we examined how pCO₂ and pCH₄ changed withcatchment size along two rivers (ca. 60 km stretches in both riverscorresponding to increases in basin size from 1.7–477km² and 2.5–275 km²). pCO₂and pCH₄ showed opposite trends, with pCO₂decreasing ca. 50% along the rivers, whereas pCH₄roughly doubled in concentration downstream. These opposing shifts resultedin a nearly five-fold increase of pCH₄:pCO₂along the rivers from a low of 0.012 in headwaters to a high of 0.266 65-kmdownstream. pCO₂ likely declines moving downstream asgroundwater influences on stream chemistry decreases, whereaspCH₄ may increase as the prevalence of anoxia in riversexpands due to finer-grained sediments and reduced hydrologic exchange withoxygenated surface water.