Ecological Drivers of Species Distributions and Niche Overlap for Three Subterranean Termite Species in the Southern Appalachian Mountains, USA

Pushed Northward by Climate Change: Range Shifts With a Chance of Co-occurrence Reshuffling in the Forecast for Northern European Odonates

Biodiversity is heavily influenced by ongoing climate change, which often results in species undergoing range shifts, either poleward or uphill. Range shifts can occur provided suitable habitats exist within reach. However, poleward latitudinal shifts might be limited by additional abiotic or biotic constraints, such as increased seasonality, photoperiod patterns, and species interactions. To gain insight into the dynamics of insect range shifts at high latitudes, we constructed ecological niche models (ENMs) for 57 Odonata species occurring in northern Europe. We used citizen science data from Sweden and present-day climatic variables covering a latitudinal range of 1,575 km. Then, to measure changes in range and interactions among Odonata species, we projected the ENMs up to the year 2080. We also estimated potential changes in species interactions using niche overlap and co-occurrence patterns. We found that most Odonata species are predicted to expand their range northward. The average latitudinal shift is expected to reach 1.83 and 3.25 km y-1 under RCP4.5 and RCP8.5 scenarios, respectively, by 2061-2080. While the most warm-dwelling species may increase their range, our results indicate that cold-dwelling species will experience range contractions. The present-day niche overlap patterns among species will remain largely the same in the future. However, our results predict changes in co-occurrence patterns, with many species pairs showing increased co-occurrence, while others will no longer co-occur because of the range contractions. In sum, our ENM results suggest that species assemblages of Odonata-and perhaps insects in general-in northern latitudes will experience great compositional changes.

Predicting the potential distribution of four endangered holoparasites and their primary hosts in China under climate change

Climate change affects parasitic plants and their hosts on distributions. However, little is known about how parasites and their hosts shift in distribution, and niche overlap in response to global change remains unclear to date. Here, the potential distribution and habitat suitability of four endangered holoparasites and their primary hosts in northern China were predicted using MaxEnt based on occurrence records and bioclimatic variables. The results indicated that (1) Temperature annual range (Bio7) and Precipitation of driest quarter (Bio17) were identified as the common key climatic factors influencing distribution (percentage contribution > 10%) for Cynomorium songaricum vs. Nitraria sibirica (i.e., parasite vs. host); Temperature seasonality (Bio4) and Precipitation of driest month (Bio14) for Boschniakia rossica vs. Alnus mandshurica; Bio4 for Cistanche deserticola vs. Haloxylon ammodendron; Precipitation of warmest quarter (Bio18) for Cistanche mongolica vs. Tamarix ramosissima. Accordingly, different parasite-host pairs share to varying degree the common climatic factors. (2) Currently, these holoparasites had small suitable habitats (i.e., moderately and highly) (0.97-3.77%), with few highly suitable habitats (0.19-0.81%). Under future scenarios, their suitable habitats would change to some extent; their distribution shifts fell into two categories: growing type (Boschniakia rossica and Cistanche mongolica) and fluctuating type (Cynomorium songaricum and Cistanche deserticola). In contrast, the hosts' current suitable habitats (1.42-13.43%) varied greatly, with highly restricted suitable habitats (0.18-1.00%). Under future scenarios, their suitable habitats presented different trends: growing type (Nitraria sibirica), declining type (Haloxylon ammodendron) and fluctuating type (the other hosts). (3) The niche overlaps between parasites and hosts differed significantly in the future, which can be grouped into two categories: growing type (Boschniakia rossica vs. Alnus mandshurica, Cistanche mongolica vs. Tamarix ramosissima), and fluctuating type (the others). Such niche overlap asynchronies may result in severe spatial limitations of parasites under future climate conditions. Our findings indicate that climate factors restricting parasites and hosts' distributions, niche overlaps between them, together with parasitic species identity, may jointly influence the suitable habitats of parasitic plants. Therefore, it is necessary to take into account the threatened holoparasites themselves in conjunction with their suitable habitats and the parasite-host association when developing conservation planning in the future.

Belowground community turnover accelerates the decomposition of standing dead wood

Standing dead trees (snags) decompose more slowly than downed dead wood and provide critical habitat for many species. The rate at which snags fall therefore influences forest carbon dynamics and biodiversity. Fall rates correlate strongly with mean annual temperature, presumably because warmer climates facilitate faster wood decomposition and hence degradation of the structural stability of standing wood. These faster decomposition rates coincide with turnover from fungal-dominated wood decomposer communities in cooler forests to co-domination by fungi and termites in warmer regions. A key question for projecting forest dynamics is therefore whether temperature effects on wood decomposition arise primarily because warmer conditions facilitate faster decomposer metabolism, or are also influenced indirectly by belowground community turnover (e.g. termites exert additional influence beyond fungal-plus-bacterial mediated decomposition). To test between these possibilities, we simulate standing dead trees with untreated, wooden posts and follow them in the field across five years at 12 sites, before measuring buried, soil-air interface and aerial post sections to quantify wood decomposition and organism activities. High termite activities at the warmer sites are associated with rates of post fall that are 3-times higher than at the cooler sites. Termites primarily consume buried wood, with decomposition rates greatest where termite activities are highest. However, where higher microbial and termite activities co-occur, they appear to first compensate for one another and then slow decomposition rates at their highest activities, suggestive of interference competition. If the range of microbial- and termite co-domination of wood decomposer communities expands under climate warming, our data suggest that expansion will accelerate snag fall with consequent effects on forest carbon cycling and biodiversity in forests previously dominated by microbial decomposers.

Identification of Reticulitermes Subterranean Termites (Blattodea: Rhinotermitidae) in the Eastern United States Using Inter-Simple Sequence Repeats

In the eastern United States, there are nine species of subterranean termites in three genera: Reticulitermes (six species), Coptotermes (two species), and Prorhinotermes (one species). These species serve as important ecological players by decomposing cellulose material, and some are important structural pests. Many of these species are difficult to discriminate morphologically and require examining the reproductive or soldier castes, which can be difficult to collect. While some genetic tools have been developed for species identification, they are often expensive and time-consuming. To help facilitate identification, we developed a more cost-effective and rapid genetic method to identify Reticulitermes species by screening 10 PCR primers that amplified inter-simple sequence repeats (ISSRs) in other termite species. From these, one primer was amplified in all five focal Reticulitermes species and contained conserved, species-specific fragments. We further screened this identification method on samples of each species covering a diversity of mitochondrial DNA haplotypes and localities. This identification method utilizing ISSRs can be used to quickly identify five species of Reticulitermes subterranean termites in the eastern United States in a matter of hours, providing a useful technique for pest management as well as future ecological research.

Seasonal Activity, Spatial Distribution, and Physiological Limits of Subterranean Termites (Reticulitermes Species) in an East Texas Forest

One of the major goals of ecology is to understand how co-habiting species partition limited resources. In the eastern U.S., at least three species of Reticulitermes subterranean termites often occur in sympatry; however, little is known about how these species divide food resources. In this study, we characterized the foraging activity of Reticulitermes flavipes (Kollar), R. hageni Banks, and R. virginicus (Banks) across seasons to assess the impact of environmental conditions on resource partitioning. A field site consisting of two grids of wooden monitors was sampled monthly for 28 months. Foraging activity in all three species was correlated with the interaction of temperature and moisture. This correlation was influenced by temperature and moisture approximately equally in R. flavipes, whereas temperature contributed more to the correlation in R. hageni, and moisture contributed more in R. virginicus. These differences caused each species to preferentially forage during specific environmental conditions: R. flavipes continued foraging after high moisture events, R. hageni increased foraging under higher soil moisture, and R. virginicus increased foraging under lower soil temperatures. We attempted to explain these patterns by the species' physiological limits; however, we found no differences in upper lethal limit, desiccation, or submersion limits across species. These results add to the overall understanding of resource partitioning by emphasizing the ability of multiple species to utilize the same resource under different environmental conditions and raise questions regarding the physiological and/or behavioral mechanisms involved.

Do Termitaria Indicate the Presence of Groundwater? A Case Study of Hydrogeophysical Investigation on a Land Parcel with Termite Activity

Simple Summary

Termitaria are nests of termites built from clayey soils. These nests can protrude to several meters high above the ground-surface. They serve not only as habitats for termites but also as foraging hotspots for grazing and browsing animals due to an increase in nutrient recycling that results in the growth of nutrient-rich vegetation around termitaria. There have been suggestions that a relationship exists between termitaria and groundwater due to the high demand of water by termite colonies for their nest building, to maintain high humidity and for their metabolism. However, few studies are available to directly or indirectly indicate this relationship. In this study, effort was made to investigate the direct relationship between termitaria and groundwater and to further answer the question on whether termitaria can indicate the presence of groundwater. A small parcel of land with a termitarium was selected for this study where nine resistivity soundings were made with one at the foot of the termitarium. The result obtained indicated a suitable geoelectrical signature around the termitarium and the integration of six geoelectrical parameters revealed the termitarium as falling in the middle of the most suitable zone of groundwater and hence can be used as a biomarker.

Abstract

Termite nests have long been suggested to be good indicators of groundwater but only a few studies are available to demonstrate the relationship between the two. This study therefore aims at investigating the most favourable spots for locating groundwater structures on a small parcel of land with conspicuous termite activity. To achieve this, geophysical soundings using the renowned vertical electrical sounding (VES) technique was carried out on the gridded study area. A total of nine VESs with one at the foot of a termitarium were conducted. The VES results were interpreted and assessed via two different techniques: (1) physical evaluation as performed by drillers in the field and (2) integration of primary and secondary geoelectrical parameters in a geographic information system (GIS). The result of the physical evaluation indicated a clear case of subjectivity in the interpretation but was consistent with the choice of VES points 1 and 6 (termitarium location) as being the most prospective points to be considered for drilling. Similarly, the integration of the geoelectrical parameters led to the mapping of the most prospective groundwater portion of the study area with the termitarium chiefly in the center of the most suitable region. This shows that termitaria are valuable landscape features that can be employed as biomarkers in the search of groundwater.

Hight S, Varone L. Ecological Niche Modeling to Calculate Ideal Sites to Introduce a Natural Enemy: The Case of Apanteles opuntiarum (Hymenoptera: Braconidae) to Control Cactoblastis cactorum (Lepidoptera: Pyralidae) in North America

The cactus moth, Cactoblastis cactorum (Berg) (Lepidoptera: Pyralidae), is an invasive species in North America where it threatens Opuntia native populations. The insect is expanding its distribution along the United States Gulf Coast. In the search for alternative strategies to reduce its impact, the introduction of a natural enemy, Apanteles opuntiarum Martínez and Berta (Hymenoptera: Braconidae), is being pursued as a biological control option. To identify promising areas to intentionally introduce A. opuntiarum for the control of C. cactorum, we estimated the overlap of fundamental ecological niches of the two species to predict their common geographic distributions using the BAM diagram. Models were based on native distributional data for both species, 19 bioclimatic variables, and the Maxent algorithm to calculate the environmental suitability of both species in North America. The environmental suitability of C. cactorum in North America was projected from Florida to Texas (United States) along the Gulf coastal areas, reaching Mexico in northern regions. Apanteles opuntiarum environmental suitability showed a substantial similarity with the calculations for C. cactorum in the United States. Intentional introductions of A. opuntiarum in the actual distribution areas of the cactus moth are predicted to be successful; A. opuntiarum will find its host in an environment conducive to its survival and dispersal.

Interspecific Variability of Water Storage Capacity and Absorbability of Deadwood

The aim of the study was to determine the water storage capacity and absorbability of deadwood of different tree species with varying degrees of decomposition. Coniferous (Silver fir—Abies alba Mill.) and deciduous (Common hornbeam—Carpinus betulus L., Common ash—Fraxinus excelsior L., Common alder—Alnus glutinosa Gaertn., and Common aspen—Populus tremula L.) species were selected for the research. The study focuses on the wood of dead trees at an advanced stage of decomposition. Deadwood samples were collected at the Czarna Rózga Nature Reserve in central Poland. Changes over time of the water absorbability and water storage capacity of deadwood were determined under laboratory conditions. The research confirmed the significance of the wood species and the degree of wood decomposition in shaping the water storage capacity and absorbability of deadwood in forest ecosystems. Fir wood was characterized by having the highest water storage capacity and water absorbability. Among deciduous species under analysis, aspen wood was characterized by having the highest water storage capacity and absorbability. Our research has confirmed that deadwood may be a significant reservoir of water in forests.

Correction: Hyseni, C.; Garrick, R.C. Ecological Drivers of Species Distributions and Niche Overlap for Three Subterranean Termite Species in the Southern Appalachian Mountains, USA. Insects , 10, 33

It has recently come to our attention that two of the environmental rasters we used for analyses inour study [1] were mislabeled in a raster processing pipeline [...].

The role of glacial-interglacial climate change in shaping the genetic structure of eastern subterranean termites in the southern Appalachian Mountains, USA

The eastern subterranean termite, Reticulitermes flavipes, currently inhabits previously glaciated regions of the northeastern U.S., as well as the unglaciated southern Appalachian Mountains and surrounding areas. We hypothesized that Pleistocene climatic fluctuations have influenced the distribution of R. flavipes, and thus the evolutionary history of the species. We estimated contemporary and historical geographic distributions of R. flavipes by constructing Species Distribution Models (SDM). We also inferred the evolutionary and demographic history of the species using mitochondrial (cytochrome oxidase I and II) and nuclear (endo-beta-1,4-glucanase) DNA sequence data. To do this, genetic populations were delineated using Bayesian spatial-genetic clustering, competing hypotheses about population divergence were assessed using approximate Bayesian computation (ABC), and changes in population size were estimated using Bayesian skyline plots. SDMs identified areas in the north with suitable habitat during the transition from the Last Interglacial to the Last Glacial Maximum, as well as an expanding distribution from the mid-Holocene to the present. Genetic analyses identified three geographically cohesive populations, corresponding with northern, central, and southern portions of the study region. Based on ABC analyses, divergence between the Northern and Southern populations was the oldest, estimated to have occurred 64.80 thousand years ago (kya), which corresponds with the timing of available habitat in the north. The Central and Northern populations diverged in the mid-Holocene, 8.63 kya, after which the Central population continued to expand. Accordingly, phylogeographic patterns of R. flavipes in the southern Appalachians appear to have been strongly influenced by glacial-interglacial climate change.

OPEN RESEARCH BADGES

This article has been awarded Open Materials, Open Data Badges. All materials and data are publicly accessible via the Open Science Framework at https://doi.org/10.5061/dryad.5hr7f31.