ABSTRACT Information about biological traits essential for pest management, such as species identity, diet and movement often require laborious and time‐intensive studies on pest natural history, in both laboratory and field settings. However, new agricultural pest threats are continually emerging, often requiring prompt responses with limited information. Using a combination of molecular gut content analysis and RAD‐seq, we examined the species identities, plant diet composition, and population genetic structure of an emerging and important agricultural pest in the US, the peanut burrower bug, Pangaeus bilineatus Say (Hemiptera, Cydnidae). We found that two, morphologically similar, burrowing bug species (including P. bilineatus) were commonly caught in light traps near peanut fields, one of which (Dallasiellus lugubris) was not previously considered a pest of peanut. Molecular gut content analysis revealed a wide, but somewhat distinct, variety of plants among the diets of both bug species. Surprisingly, peanut was a rare part of the diet of either species. RAD‐seq analysis revealed evidence consistent with weak isolation‐by‐distance and modest spatial genetic differentiation for both species. Together, these results suggest a potential pest complex where previously only one species was in focus. Moreover, their broad diets and spatially restricted population dispersal patterns may also explain the sporadic nature of damage that has been recorded for this potential pest complex. Responses to emerging pest challenges can benefit from insights generated by population genomics techniques, opening up new avenues for research and supporting efforts to quickly tailor management strategies for novel pests.
ABSTRACT Understanding the salinity tolerance of Helisoma anceps is crucial for its application in aquaculture systems, particularly at the Fish Conservation and Culture Laboratory (FCCL), where the species is used to maintain water quality in Delta and Longfin Smelt culture tanks. This study investigated the effects of salinity and temperature on the survival, growth, and food intake of H. anceps under non‐acclimated conditions. Adult snails were exposed to seven salinity levels (0, 2.5, 5, 7.5, 10, 12.5, and 15 ppt) at two temperatures (12°C and 16°C) for 42 days, and survival, growth, and feeding rates were analyzed using Kaplan–Meier survival analysis and linear mixed‐effects models. Results showed complete mortality at ≥ 10 ppt within 48 h, identifying a salinity tolerance limit between 7.5 and 10 ppt. Growth and food intake significantly declined with increasing salinity, while temperature modulated these effects, with higher activity and food intake observed at 16°C. Shell volume‐specific growth rate (SVSGR) was more sensitive to salinity stress than shell length‐specific growth rate (SLSGR), reflecting reduced calcification efficiency under hyperosmotic conditions. The findings classify H. anceps as a stenohaline species with limited osmoregulatory capacity and suggest that its optimal performance occurs within 0–5 ppt salinity at 16°C. These insights provide a physiological basis for managing H. anceps in smelt hatchery systems and highlight the need for careful salinity control to sustain its ecological function in aquaculture operations.
ABSTRACT Loss of anadromy in Salmonids frequently follows postglacial colonization and habitat change, a process driven by selective pressures where benefits of residency outweigh migration costs. At the end of the last Ice Age ca. 10,000 years ago, anadromous brown trout arrived in Iceland and invaded newly formed habitats. Some populations became isolated in headwaters early after the ice retreated, presumably accelerating local adaptation and the evolution of residency. In this study, we assessed the genetic relatedness and diversity of brown trout on a countrywide scale to decipher the number of unique populations and their connectivity. We tested for gene flow from headwaters and assessed effects of isolation and adaptation. We genotyped 600 individuals from 40 locations using ddRADseq, identifying 2946 putative neutral SNPs. We identified 16 groups of genetically similar individuals (genetic clusters), five of which were primarily composed of anadromous individuals. On a large scale, the genetic variation and relatedness of trout populations reflect the geography of waterways while within watersheds the topography, for example, the presence of waterfalls and lakes, is key. Counterintuitively, downstream gene flow from isolated headwater populations was only seen in small river populations whereas gene flow from large lake populations appears negligible. Using outlier SNPs, we identified several hundred loci associated with temperature and habitat type (i.e., lake vs. river). Temperature‐associated markers mapped to loci associated with immune response, lipid metabolism and transmembrane protein genes. Our results highlight the effects of isolation on genetic diversity in headwater populations and the importance of identifying unique populations in conservation efforts.
ABSTRACT Understanding how taxa diverge within their ecological niches is essential for revealing mechanisms driving biodiversity and biogeographic patterns, particularly in regions with complex environmental gradients. Ecological niche dynamics have profound implications for speciation and species distributions, yet remain underexplored in freshwater organisms. Here, we investigated ecological niche variation among clades of Aegla (Aeglidae), a diverse freshwater crustacean genus endemic to southern South America, to uncover links between niche differentiation and lineage diversification. Using MaxEnt to build niche models with climatic and elevation variables, we assessed niche overlap and similarity in environmental space via PCA‐env, Hellinger's I, and Schoener's D metrics, complemented by equivalence and similarity tests. We found pronounced niche divergence among Aegla clades, characterized by distinct climatic preferences and low‐to‐moderate pairwise overlap. Niche equivalence tests rejected conservatism in all comparisons. This divergence is consistent with the combined effects of geographical isolation among drainage basins and regional climatic heterogeneity, which may have restricted dispersal and promoted the independent occupation of contrasting environmental conditions. These patterns suggest that ecological differentiation, together with historical geographic isolation, is closely associated with diversification within the group. Our results demonstrate that ecological adaptation has likely contributed to diversification in Aegla, highlighting niche divergence as an important component of freshwater biodiversity. These insights emphasize the sensitivity of such taxa to ongoing environmental changes and advance our understanding of ecological processes in shaping evolutionary patterns in South American aquatic systems.
ABSTRACT The success of an invasive species is driven by its interactions with both native species and co‐occurring invaders. These interactions can range from competitive exclusion to mutual facilitation. However, the factors that govern the direction of species interaction outcomes remain poorly understood in invasive systems, including their environmental dependency. We performed species interactions experiments between two co‐occurring invasive blow flies: Calliphora stygia and Lucilia sericata. We varied both total larval density (n = 10, 20, 30, 50) and relative species ratios (100%, 70%, 50%, 30%) and measured outcomes in the form of adult emergence success and adult body size. We found that interaction outcomes varied by species. For intraspecific experiments, C. stygia experienced more pronounced effects of competition, with a more than 2.4‐fold greater reduction in body size between low (n = 10) and high (n = 50) densities than experienced by L. sericata between the same densities. Calliphora stygia also experienced reduced adult emergence at n = 30 and n = 50, while L. sericata emergence was not affected. However, interspecific competition drove contrasting density‐dependent species‐specific responses. At low density interspecific ratios of 70% and 50%, female C. stygia performance reflected facilitation (i.e., increased body size relative to intraspecific competition), with no effect for L. sericata, while increasing density shifted interaction dynamics towards competition (i.e., interspecific and intraspecific effects became comparable) for both body size and adult emergence under all species ratios except 50C:50 L for males, where C. stygia body size decreased. In contrast, L. sericata performed worse under all high density interspecific conditions relative to intraspecific competition when measuring body size, suggesting stronger interspecific effects, regardless of species ratios. The asymmetric response of these two co‐occurring blow flies highlights the nuance of co‐invader interactions: competition outcomes between invaders are not fixed but rather strongly shaped by both density and species balance.
