Evaluation of species distribution models by resampling of sites surveyed a century ago by Joseph Grinnell

Species distribution models (SDMs) are commonly applied to predict species’ responses to anticipated global change, but lack of data from future time periods precludes assessment of their reliability. Instead, performance against test data in the same era is assumed to correlate with accuracy in the future. Moreover, high‐confidence absence data is required for testing model accuracy but is often unavailable since a species may be present when undetected. Here we evaluate the performance of eight SDMs trained with historic (1900–1939) or modern (1970–2009) climate data and occurrence records for 18 mammalian species. Models were projected to the same or the opposing time period and evaluated with data obtained from surveys conducted by Joseph Grinnell and his colleagues in the Sierra Nevada of California from 1900 to 1939 and modern resurveys from 2003 to 2011. Occupancy modeling was used to confidently assign absences at test sites where species were undetected. SDMs were evaluated using species’ presences combined with this high‐confidence absence (HCA) set, a low‐confidence set in which non‐detections were assumed to indicate absence (LCA), and randomly located ‘pseudoabsences’ (PSA). Model performance increased significantly with the quality of absences (mean AUC ± SE: 0.76 ± 0.01 for PSA, 0.79 ± 0.01 for LCA, and 0.81 ± 0.01 for HCA), and apparent differences between SDMs declined as the quality of test absences increased. Models projecting across time performed as well as when projecting within the same time period when assessed with threshold‐independent metrics. However, accuracy of presence and absence predictions sometimes declined in cross‐era projections. Although most variation in performance occurred among species, autecological traits were only weakly correlated with model accuracy. Our study indicates that a) the quality of evaluation data affects assessments of model performance; b) within‐era performance correlates positively but unreliably with cross‐era performance; and c) SDMs can be reliably but cautiously projected across time.     

Impact of crimson clover dying mulch on two eggplant insect herbivores

Eggplant Solanum melongena L., is often colonized by two early season insect defoliators. The Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), and flea beetles Epitrix spp., emerge from their overwintering sites in early spring and seek out emerging host plants such as eggplant. During the 2009 and 2010 growing season, field studies were conducted to investigate the impact of inter‐planting eggplant into a crimson clover (CC), Trifolium incarnatum L., winter cover crop on populations of flea beetles, CPB and their associated arthropod predators. The experiment consisted also of two levels of insecticide usage such as an application of azadirachtins plus pyrethrins followed by several applications of spinosad or no insecticide sprays as subplot treatments. During both study years, significantly fewer (adults, larvae and egg masses) were found on eggplant inter‐planted into CC than in bare‐ground (BG) eggplant plots. Although flea beetle abundance was greater in BG eggplant during 2010, they appeared to be less influenced by the presence of CC than were CPB. Additionally, there was no apparent impact of insecticide treatment on CPB populations on eggplant inter‐planted into CC. However, there was a decline in CPB following treatments with insecticides in BG eggplant plots. This suggests that a winter cover crop such as CC can be used to help manage CPB in eggplant, however, using this tactic in tandem with insecticide sprays may not result in greater CPB management.     

Dopaminergic Regulation of Circadian Food Anticipatory Activity Rhythms in the Rat

Circadian activity rhythms are jointly controlled by a master pacemaker in the hypothalamic suprachiasmatic nuclei (SCN) and by food-entrainable circadian oscillators (FEOs) located elsewhere. The SCN mediates synchrony to daily light-dark cycles, whereas FEOs generate activity rhythms synchronized with regular daily mealtimes. The location of FEOs generating food anticipation rhythms, and the pathways that entrain these FEOs, remain to be clarified. To gain insight into entrainment pathways, we developed a protocol for measuring phase shifts of anticipatory activity rhythms in response to pharmacological probes. We used this protocol to examine a role for dopamine signaling in the timing of circadian food anticipation. To generate a stable food anticipation rhythm, rats were fed 3h/day beginning 6-h after lights-on or in constant light for at least 3 weeks. Rats then received the D2 agonist quinpirole (1 mg/kg IP) alone or after pretreatment with the dopamine synthesis inhibitor α-methylparatyrosine (AMPT). By comparison with vehicle injections, quinpirole administered 1-h before lights-off (19h before mealtime) induced a phase delay of activity onset prior to the next meal. Delay shifts were larger in rats pretreated with AMPT, and smaller following quinpirole administered 4-h after lights-on. A significant shift was not observed in response to the D1 agonist SKF81297. These results provide evidence that signaling at D2 receptors is involved in phase control of FEOs responsible for circadian food anticipatory rhythms in rats.     

Photic and Pineal Modulation of Food Anticipatory Circadian Activity Rhythms in Rodents

Restricted daily feeding schedules entrain circadian oscillators that generate food anticipatory activity (FAA) rhythms in nocturnal rodents. The location of food-entrainable oscillators (FEOs) necessary for FAA remains uncertain. The most common procedure for inducing circadian FAA is to limit food access to a few hours in the middle of the light period, when activity levels are normally low. Although light at night suppresses activity (negative masking) in nocturnal rodents, it does not prevent the expression of daytime FAA. Nonetheless, light could reduce the duration or magnitude of FAA. If so, then neural or genetic ablations designed to identify components of the food-entrainable circadian system could alter the expression of FAA by affecting behavioral responses to light. To assess the plausibility of light as a potential mediating variable in studies of FAA mechanisms, we quantified FAA in rats and mice alternately maintained in a standard full photoperiod (12h of light/day) and in a skeleton photoperiod (two 60 min light pulses simulating dawn and dusk). In both species, FAA was significantly and reversibly enhanced in the skeleton photoperiod compared to the full photoperiod. In a third experiment, FAA was found to be significantly attenuated in rats by pinealectomy, a procedure that has been reported to enhance some effects of light on behavioral circadian rhythms. These results indicate that procedures affecting behavioral responses to light can significantly alter the magnitude of food anticipatory rhythms in rodents.     

Phylogenetic position of the acariform mites: sensitivity to homology assessment under total evidence

Background  

Mites (Acari) have traditionally been treated as monophyletic, albeit composed of two major lineages: Acariformes and Parasitiformes. Yet recent studies based on morphology, molecular data, or combinations thereof, have increasingly drawn their monophyly into question. Furthermore, the usually basal (molecular) position of one or both mite lineages among the chelicerates is in conflict to their morphology, and to the widely accepted view that mites are close relatives of Ricinulei.     

Basal lamina and the organization of neuromuscular synapses

Fast chemical synapses are comprised of presynaptic and postsynaptic specializations precisely aligned across a protein-filled synaptic cleft. At the vertebrate neuromuscular junction (NMJ), the synaptic cleft contains a structured form of extracellular matrix known as a basal lamina (BL). Synaptic BL is molecularly differentiated from the BL that covers the extrasynaptic region of the myofiber. This review summarizes current understanding of the morphology, composition, and function of the synaptic BL at the vertebrate NMJ. Considerable evidence supports the conclusion that the synaptic BL organizes and maintains pre- and postsynaptic specializations during development and regeneration, and promotes robust neurotransmission in the adult.