1. Understanding how ecosystem engineers influence other organisms has long been a goal of ecologists. Woodpeckers select nesting sites with high food availability and will excavate and then abandon multiple cavities throughout their lifetime. These cavities are crucial to secondary cavity nesting birds (SCB) that are otherwise limited by the availability of naturally occurring cavities. 2. Our study examined the influence of food resources on the nest site location and home-range size of woodpeckers, and the subsequent influence of woodpeckers on the nesting success of SCB. 3. Using five years of avian point count data to locate golden-fronted woodpeckers (GFWO), we correlated insect availability with GFWO home range size, determined differences in insect availability between GFWO occupied and unoccupied sites, and compared nesting success for the GFWO and common SCB in south Texas. We used model averaging to fit species-specific logistic regression models to predict nest success based on cavity metrics across all species. 4. Sites occupied by GFWO had a higher biomass of insects in orders Coleoptera, Hymenoptera, and Orthoptera than unoccupied sites, and there was a negative correlation between the availability of these insect orders and home-range size. GFWO nest success increased with vegetation cover and lower levels of tree decay. SCB had higher levels of nesting success in abandoned GFWO, and in trees with lower levels of nest tree decay. 5. Our results suggest that SCB may be drawn to nest in abandoned woodpecker cavities where they have higher rates of nest success compared to natural cavities. Additionally, the prevalence for GFWO to excavate cavities in trees with lower levels of decay contradicts previous literature, and may indicate a novel temperature trade-off, with live trees requiring more energy to excavate, but providing increased protection from high breeding season temperatures in arid and semi-arid areas.
The White Sands pupfish (Cyprinodon tularosa), endemic to New Mexico in Southwestern North America, is of conservation concern due in part to invasive species, chemical pollution, and groundwater withdrawal. Herein, we developed a high quality draft reference genome and use it to provide biological insights into the evolution and conservation of C. tularosa. Specifically, we localized microsatellite markers previously used to demarcate Evolutionary Significant Units, evaluated the possibility of introgression into the C. tularosa genome, and compared genomic diversity among related species. The de novo assembly of PacBio Sequel II error-corrected reads resulted in a 1.08Gb draft genome with a contig N50 of 1.4Mb and 25,260 annotated protein coding genes, including 95% of the expected Actinopterigii conserved orthologs. Many of the previously described C. tularosa microsatellite markers fell within or near genes and exhibited a pattern of increased heterozygosity near genic areas compared to those in intergenic regions. Genetic distances between C. tularosa and the widespread invasive species C. variegatus, which diverged ~1.6-4.7 MYA, were 0.027 (nuclear) and 0.022 (mitochondrial). Nuclear alignments revealed putative tracts of introgression that merit further investigation. Genome-wide heterozygosity was markedly lower in C. tularosa compared to estimates from related species, likely because of smaller long-term effective population sizes constrained by their isolated and limited habitat. These population inferences, generated from our new genome assembly, provide insights into the long term and contemporary White Sands pupfish populations that are integral to future management efforts.