Distributed under Creative Commons CC-BY 4.0 OPEN ACCESS Deer herbivory reduces web-building spider abundance by simplifying forest vegetation structure

ABSTRACT Indirect ecological effects are a common feature of ecological systems, arising when one species affects interactions among two or more other species. We examined how browsing by white-tailed deer (Odocoileus virginianus) indirectly affected the abundance and composition of a web-building spider guild through their effects on the structure of the ground and shrub layers of northern hardwood forests. We examined paired plots consisting of deer-free and control plots in the Allegheny Plateau region Pennsylvania and Northern Highlands region of Wisconsin. We recorded the abundance of seven types of webs, each corresponding to a family of web-building spiders. We quantified vegetation structure and habitat suitability for the spiders by computing a web scaffold availability index (WSAI) at 0.5 m and 1.0 m above the ground. At Northern Highlands sites, we recorded prey availability. Spider webs were twice as abundant in deer-free plots compared to control plots, while WSAI was 7-12 times greater in deerfree plots. Prey availability was lower in deer-free plots. With the exception of funnel web-builders, all spider web types were significantly more abundant in deer-free plots. Both deer exclusion and the geographic region of plots were significant predictors of spider community structure. In closed canopy forests with high browsing pressure, the low density of tree saplings and shrubs provides few locations for web-building spiders to anchor webs. Recruitment of these spiders may become coupled with forest disturbance events that increase tree and shrub recruitment. By modifying habitat structure, deer appear to indirectly modify arthropod food web interactions. As deer populations have increased in eastern North America over the past several decades, the effects of deer on web-building spiders may be widespread

Deer herbivory reduces web-building spider abundance by simplifying forest vegetation structure

Indirect ecological effects are a common feature of ecological systems, arising when one species affects interactions among two or more other species. We examined how browsing by white-tailed deer (Odocoileus virginianus) indirectly affected the abundance and composition of a web-building spider guild through their effects on the structure of the ground and shrub layers of northern hardwood forests. We examined paired plots consisting of deer-free and control plots in the Allegheny Plateau region Pennsylvania and Northern Highlands region of Wisconsin. We recorded the abundance of seven types of webs, each corresponding to a family of web-building spiders. We quantified vegetation structure and habitat suitability for the spiders by computing a web scaffold availability index (WSAI) at 0.5 m and 1.0 m above the ground. At Northern Highlands sites, we recorded prey availability. Spider webs were twice as abundant in deer-free plots compared to control plots, while WSAI was 7–12 times greater in deerfree plots. Prey availability was lower in deer-free plots. With the exception of funnel web-builders, all spider web types were significantly more abundant in deer-free plots. Both deer exclusion and the geographic region of plots were significant predictors of spider community structure. In closed canopy forests with high browsing pressure, the low density of tree saplings and shrubs provides few locations for web-building spiders to anchor webs. Recruitment of these spiders may become coupled with forest disturbance events that increase tree and shrub recruitment. By modifying habitat structure, deer appear to indirectly modify arthropod food web interactions. As deer populations have increased in eastern North America over the past several decades, the effects of deer on web-building spiders may be widespread

CHIPS-Child: Testing the developmental programming hypothesis in the offspring of the CHIPS trial

Objectives: As a follow-up to the CHIPS trial (Control of Hypertension In Pregnancy Study) of ‘less tight’ (versus ‘tight’) control of maternal blood pressure in pregnancy, CHIPS-Child investigated potential developmental programming of maternal blood pressure control in pregnancy, by examining measures of postnatal growth rate and hypothalamic-pituitary adrenal (HPA) axis activation. Methods: CHIPS follow-up was extended to 12 ± 2 months corrected post-gestational age for anthropometry (weight, length, head/waist circumference). For eligible children with consent for a study visit, we collected biological samples (hair/buccal samples) to evaluate HPA axis function (hair cortisol levels) and epigenetic change (DNA methylation analysis of buccal cells). The primary outcome was ‘change in z-score for weight’ between birth and 12 ± 2 mos. Secondary outcomes were hair cortisol and genome-wide DNA methylation status. Results: Of 683 eligible babies, 183 (26.8%) were lost to follow-up, 83 (12.2%) declined, 3 (0.4%) agreed only to ongoing contact, and 414 (60.6%) consented. 372/414 (89.9%) had weight measured at 12mos. In ‘less tight’ (vs. ‘tight’) control, the primary outcome was similar [−0.26 (−0.53, +0.01); p = 0.14, padjusted = 0.06]; median (95% confidence interval) hair cortisol (N = 35 samples) was lower [−496 (−892, −100) ng/g; p = 0.02], and buccal swab DNA methylation (N = 16 samples) was similar. No differences in growth rate could be demonstrated up to 5 years. Conclusions: Results demonstrate no compelling evidence for developmental programming of growth or the HPA axis. Clinicians should look to the clinical findings of CHIPS to guide practice. Researchers should seek to replicate these findings and extend outcomes to paediatric blood pressure and neurodevelopment.</p