Department of Ecology and Evolutionary Biology

Fucus distichus, a rockweed common to the mid-intertidal shoreline within the San Francisco Estuary (previously known as F. gardneri), was injured during the Cosco Busan oil spill in November 2007 and subsequent clean-up actions. Restoration planning activities are underway to help recover F. distichus at sites within central San Francisco Bay where damage occurred. As a first step, we conducted shoreline surveys during the summers of 2012–2013 to map the occurrence of this rockweed. Of the 151.73 km of rocky shoreline within the central bay, F. distichus covered 32.16 km of shoreline. The alga generally occurred in narrow bands but formed expansive beds at locations with natural, flat bedrock benches. We also observed F. distichus on artificial substrata such as seawalls and riprap, but not on pilings. Samples of F. distichus from 11 sites throughout the central / east San Francisco Bay were genetically analyzed (microsatellite genotyping). The populations analyzed (1) had low genetic diversity, (2) the frequency of homozygotes was higher than expected (suggesting high inbreeding), and (3) also displayed geographic population structure, in part driven by very small differences in the midst of extremely low within-population genetic diversity. However, these genetic data do not raise concerns for restoration methods in terms of choosing donor populations and mixing F. distichus from different sites within the central bay. The choice of donor populations should be based on practical criteria for effective restoration; individuals will nonetheless be taken from locations as nearby to donor sites as possible. Various locations throughout the central San Francisco Bay are composed of cobble or small riprap that are populated with F. distichus, which could provide efficient means of translocating rockweed for future restoration activities.

Genetic assessments serve as powerful tools to evaluate the effects of anthropogenic habitat fragmentation on natural populations. In the Klamath River Basin, construction of four dams from 1912 to 1962 had a profound impact on the distribution of anadromous fishes, blocking access to over 751 river kilometers of critical habitat. To characterize the genetic diversity and connectivity among Oncorhynchus mykiss in the basin prior to the historic removal of the four dams in 2024, we genotyped 2466 samples at 193 presumably neutral and 105 putatively adaptive markers. Using complementary population genetic analyses, we found a clear division between coastal and inland O. mykiss lineages located primarily downstream and upstream of the outlet of Upper Klamath Lake, and little genetic structure associated with dams. Further, we detected distinct inland and coastal genetic lineages upstream of the lake outlet supporting the hypothesis that ancestral inland O. mykiss were secondarily invaded by a coastal lineage. We found that neutral genetic diversity was significantly greater in collections consisting primarily of anadromous O. mykiss compared to collections of adfluvial, fluvial, and resident fish while genetic diversity was significantly lower in adfluvial collections. Based on the chromosome Omy5 markers associated with anadromous/resident phenotypes, we found that anadromous and heterozygous genotypes were more prevalent downstream of the lake outlet while resident genotypes were prevalent upstream of the outlet. Based on the chromosome Omy28 markers associated with adult migration timing, we found that late-migration timing and heterozygous genotypes were numerous downstream of the lake outlet while early-migration timing genotypes were prevalent upstream of the outlet. The results of our population genetic analyses highlight the genetic diversity and structure of O. mykiss in the Klamath River Basin and will serve as a critical baseline for future assessments post dam removal.

The mechanisms by which animals navigate during long ocean migrations to specific targets remain equivocal despite over a century of investigation. To address this question, we developed and deployed a new tag that allowed the compass heading of migrators to be remotely relayed via satellite. On transocean migrations (>1000 kilometers and mean duration 27.5 days) between nesting and foraging sites, green turtles (Chelonia mydas) tended to perform sections of travel with a consistent compass heading, even if that led them off course, before reorienting. That migrating turtles did not continuously fine-tune their heading but rather made occasional reorientations is consistent with the suggestion that they use geomagnetic signposts, or other crude maps, to facilitate occasional course corrections.

A longstanding but untested hypothesis proposes that reduced bee visitation in tropical montane cloud forests has repeatedly driven the evolution of hummingbird pollination. Here, we test whether recently diverged bee and hummingbird pollination syndromes in two sister species are adapted to their pollination environments, and whether this reflects declining bee activity at higher elevations. Alternatively, we ask whether higher pollen transfer efficiency drives adaptation to hummingbirds regardless of bee availability. We measured visitation and per-visit efficiency to estimate pollinator effectiveness and conducted reciprocal translocations of Costus kuntzei, with ancestral bee pollination, and Costus wilsonii, with derived hummingbird pollination, across an elevational gradient in Costa Rica, including sites within and outside each species' range and at their elevational boundary. In their ranges, the species are specialized on bees or hummingbirds. However, pollinator effectiveness was higher for hummingbird-pollinated C. wilsonii because of greater per-visit efficiency, despite bee-pollinated C. kuntzei experiencing higher visitation. In reciprocal translocations, C. kuntzei showed uniform bee visitation across habitats, whereas hummingbird visitation increased with elevation for C. wilsonii. Our results show that floral adaptation to hummingbird pollination is likely driven by higher hummingbird visitation in montane environments combined with greater per-visit efficiency, rather than declining bee visitation with elevation.

Bull kelp, Nereocystis luetkeana, is a northeastern Pacific kelp with a broad distribution from Alaska to central California. Its population declines have caused severe concerns in northern California, the Salish Sea in Washington, and recently in some populations in Oregon. Despite bull kelp's accumulated ecological and physiological studies, an assembled and annotated genomic reference was still unavailable. Here, we report the complete and annotated genome of N. luetkeana, produced by the California Conservation Genomics Project (CCGP), which aims to reveal genomic diversity patterns across California by sequencing the complete genomes of approximately 150 carefully selected species. The genome was assembled into 1,562 scaffolds with 449.82 Mb, 80× of coverage, and 22,952 gene models. BUSCO assembly showed a completeness score of 72% for the stramenopiles gene set. The mitochondria and chloroplast genome sequences have 37 Kb and 131 Mb, respectively. The orthology analysis between 10 Phaeophycean genomes showed 1,065 expanded and 286 unique orthogroups for this species. Pairwise comparisons showed 542 orthogroups present only in N. luetkeana and Macrocystis pyrifera, another large-body kelp. The enrichment analysis of these orthogroups showed important functions related to central metabolism and signaling due to ATPase enrichment in these two species. This genome assembly will provide an essential resource for the ecology, evolution, conservation, and breeding of bull kelp.

ABSTRACT: Aim: Environmental heterogeneity shapes species diversity by creating ecological niches (habitat heterogeneity hypothesis). Yet its role in driving behavioural diversity within species remains only partially understood. Behavioural diversity enhances a population's ability to exploit ecological niches and adapt to environmental change, making it critical to understand how behaviour is shaped by environmental factors. Here we test whether spatial and temporal heterogeneity predict behavioural diversity at population and individual levels across species and environments. Location: Global. Methods: We synthesised biologging data from five species of sea lions (15 colonies, 370 individuals, ~927,000 dives) to test the relationship between population‐level behavioural variation and individual specialisation/flexibility metrics with bathymetric roughness, mean chlorophyll and interannual chlorophyll variability utilising GLMMs. Results: We provide large‐scale, multi‐species evidence that environmental heterogeneity drives behavioural diversity. We show that populations foraging in structurally complex habitats and with greater resource variability exhibited more diverse dive and foraging behaviour, demonstrating that environmental heterogeneity, both in space and time, is associated with higher behavioural diversity. While habitat complexity fostered population‐level variation, environments with low productivity favoured specialisation on the individual level, suggesting a shift from generalist to specialist strategies under resource limitation. Main Conclusions: The consistent pattern between environmental heterogeneity and population‐level behavioural diversity across species and environments suggests, in combination with observations from previous studies, a fundamental principle extending beyond species and habitat borders. We therefore suggest broadening the habitat heterogeneity hypothesis from species richness to within‐species variation. Our findings underscore two important conservation considerations: (1) conserving habitat complexity to help maintain behavioural diversity; and (2) prioritising protection for populations in low‐heterogeneity environments, where reduced behavioural flexibility may increase vulnerability to environmental change.

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Climate change threatens biodiversity when species cannot tolerate, adapt to, or track shifting environmental conditions to stay within their climatic niches. A major unresolved question is whether and how species genetic diversity modulates these dynamics, buffering against range contractions or facilitating range expansions. To test this, we integrated the largest global databases of species range shifts and genetic diversity, encompassing 4673 range shift estimates for 1888 species with available genetic data, including insects, arachnids, birds, fish, and plants. We found that range shifting rates were significantly shaped by the interaction of genetic diversity and climate change velocity. Under rapid warming, species with higher genetic diversity exhibited reduced trailing edge contractions, likely reflecting enhanced evolutionary potential or reduced vulnerability to drift. Under moderate warming, species with higher genetic diversity shifted more rapidly at leading edges and range centroids, consistent with greater colonisation ability. Our study provides evidence that genetic diversity potentially enables persistence at the trailing edge and colonisation at the leading edge, with the magnitude of these effects varying depending on the velocity of climate change.