ABSTRACT In many animals, sexual differences are predominantly determined by sex chromosomes and therefore understanding the underlying evolutionary mechanisms that affect these chromosomes is crucial. Most studies on sex chromosome evolution have employed model organisms with ancient sex chromosome systems, which have already undergone evolutionary degradation thereby hindering the detection of early evolutionary processes. Androdioecious crustaceans in the genus Eulimnadia have a unique sex‐determining system that allows examination of evolutionary models of early sex chromosome evolution. In typical ZW sex chromosome systems, the Z is usually homogametic (i.e., ZZ) and the W is heterogametic (i.e., ZW), the latter being prone to long‐term degeneration due to a lack of recombination. In Eulimnadia texana , both Z and W chromosomes are found in homogametic form (i.e., ZZ and WW) retarding the buildup of deleterious recessive alleles thereby keeping these chromosomes in the “proto‐sex chromosome” stage of evolutionary development. Therefore, the E. texana system allows exploration of the early stages of W and Z sex chromosome development. Although there is a high‐quality assembly of WW hermaphrodites, there is no complementary high‐quality male (ZZ) genome assembly yet for E. texana . In the current study, we generate PacBio HiFi sequencing data from a ZZ male, construct a contamination‐filtered de novo genome assembly, and then scaffold this assembly against the WW hermaphrodite reference. The de novo ZZ contig assembly spans ~113 Mb with an N50 of 3.5 Mb and 98.1% complete Arthropoda BUSCO genes, and scaffolding against the WW reference yields a chromosome‐scale ZZ genome (12 scaffolds, total length ~113 Mb, scaffold N50 18 Mb, 0.18% gaps). Together with its gene annotation, this scaffold‐level ZZ genome complements the WW assembly and enables future comparative analyses of the Z and W proto‐sex chromosomes.
ABSTRACT Hybridization is common in wild taxa, which may cause conservation concerns if hybridization occurs following disturbance or species introductions. High throughput DNA sequencing makes genomic analysis of many individuals feasible, vastly improving and promoting more studies on hybridization. However, more precise genomic identification of hybrids has not always extended to more precise use of terminology to describe hybrid ancestry. For hybridizing species of conservation concern, it is critical to understand hybridization dynamics precisely in order to effectively manage imperiled taxa. We conducted a review of 67 representative journal articles that use the term “hybrid swarm” in reference to hybridization, as variation in the usage of the term makes it difficult to understand which biological processes are being described. We found that “hybrid swarm” is used in several contexts across studies using various methods and numbers of genetic markers, reflecting vastly different statistical power and degrees of evidence for extensive hybridization. We encourage researchers working with genomic datasets to use clearer terminology when describing hybridization outcomes. We elaborate on scenario‐specific terminology to strengthen uniformity in hybridization language, which we hope will promote more precise descriptions of hybridization and improve the clarity of future research on hybridization.
ABSTRACT Submarine groundwater discharge (SGD) is the flow of subsurface water into the ocean. To assess its impact on the Svalbard benthos, the composition of macrobenthos was investigated in relation to sediment physico‐chemical conditions. SGD has been seen to generate seep‐like ecosystems in subarctic locations through the transport of reduced chemicals such as methane. Therefore, we compared the benthos of three Svalbard fjord SGD locations to a Svalbard shelf seep location. However, contrary to our expectations, the SGD locations did not resemble the sampled cold seep. Methane was not detectable in sediment porewater, free sulfide concentrations were low, and diversity and abundance were extremely low, despite shallow water depths (40–117 m). It is possible that the combination of freshwater stress, limited chemosynthetic primary production, and high glacimarine sedimentation rates typical of glacier‐proximal fjord environments together result in an inhospitable environment for many marine benthic taxa at Svalbard fjord SGD locations. As the Arctic warms and glaciers transition from marine‐ to land‐terminating, SGD fluxes may change and the sedimentary overprint on SGD‐related ecological effects may diminish. Whether SGD will eventually emerge as an ecologically relevant process in Arctic fjord systems remains an open question, but one that will become increasingly pertinent as permafrost thaws and glaciers continue to retreat.
ABSTRACT The golden jackal ( Canis aureus ) continues to expand across Europe, yet fine‐scale behavioural data on dispersal—particularly in mountainous regions—remain scarce. Reproducing individuals are recorded further and further to the North and West of the continent, crossing major anthropogenic and natural barriers in the landscape and settling within new habitats. Since jackals are already present or at the doorstep of almost every country on the European mainland, monitoring this range expansion is of great interest to the public and policymakers. The dispersal capacity of jackals is pivotal for their current expansion across Europe. However, research on their movement patterns, particularly natal dispersal, remains limited. Here, we analysed the full dispersal trajectory of a GPS‐collared subadult male originating from the Julian Alps (Slovenia). Using T‐LoCoH utilisation distributions, Net Squared Displacement modelling and Bayesian movement models, we reconstructed its pre‐dispersal behaviour, dispersal phase and subsequent settlement. After several initial exploratory excursions, the young male left its natal home range in mid‐November 2023 and travelled a cumulative distance of 170 km (96 km straight‐line distance), overcoming natural and anthropogenic barriers along the way. After 11 days, it established a stable home range in the Austrian Malta Valley, where reproduction was later confirmed in spring 2024—the first documented case of successful settlement and breeding by a golden jackal in a subalpine environment. During dispersal, the jackal's step length increased in areas with a higher aggregation index as well as at night, suggesting more extensive movement between consecutive GPS acquisitions in more homogeneous areas and during nighttime. Our study provides the first fine‐scale GPS documentation of dispersal, settlement, and subsequent reproduction of a golden jackal in a European subalpine environment. It highlights how both natural and human‐dominated landscapes shape movement behaviour during range expansion.
ABSTRACT Genetic mating systems shape reproductive skew, mate choice, and effective population size, yet remain poorly understood in many communally breeding amphibians. We used genetic parentage analysis to examine mating structure in the alpine tree frog ( Litoria verreauxii alpina ), a Batrachochytrium dendrobatidis ( Bd ) impacted amphibian that breeds in communal aggregations. Over a 6‐week breeding season, we recorded 477 capture events involving 197 unique adults and observed 55 egg masses. Using DArTseq‐derived SNP markers and COLONY, we reconstructed mating pairs, assessed male breeding success, and estimated effective population size ( N e ). Of the 45 egg masses with at least one successfully genotyped embryo, 97.7% had a definitive sire assigned, and every egg mass with more than one genotyped embryo was assigned to a single sire. Only one sampled male and one inferred female showed evidence of multiple mates, indicating a predominantly genetically monogamous mating structure despite communal breeding. Male reproductive success was not predicted by body size, recapture frequency, or breeding‐season timing. Effective population size was low, suggesting ongoing genetic vulnerability, but relatively even reproductive contribution among breeders may help limit reproductive skew. These findings contrast with expectations for communal‐breeding frogs, where high breeding‐site encounter rates and male‐biased attendance can create opportunities for multiple mating and unequal reproductive success. More broadly, these results show how genetic parentage data can reveal unexpected mating‐system structure in disease‐impacted amphibian populations.
