Historical Ecology, Responses to Current Ecological Changes and Conservation of Australian Spiders

In response to geohistorical events from the Mesozoic through the Tertiary with contraction of mesic forest to southwestern and eastern montane and coastal regions, and expansion of woodlands and xeric shrublands, nobreak Australian spiders today comprise relict families and genera (confined to Gondwanan habitats and refuges) along with later evolved representatives which have adapted to changing environments. Tropical relicts also persist in refugia in the arid interior while some spiders (both mygalomorphs and araneomorphs) have adapted to arid conditions, mainly through specialized behaviours. Although fire has become increasingly a phenomenon of the Australian environment it is doubtful whether any spiders are adapted to fire per se. European settlement has impacted differentially on relictual and later evolved representatives; a few species, including the funnelweb (Atrax robustus) and redback spider (Latrodectus hasselti) have benefited through enhanced habitat opportunities and some species of Badumna and other genera have become synanthropic. It is suggested that conservation strategies need to consider the ecoevolutionary history of particular spiders and their natural vulnerability or resilience to environmental factors.     

Aphid colonization of spring cereals

In 1970-1, Metopolophium dirhodum, Rhopalosiphum padi and Sitobion avenae were the commonest alatae trapped from April/May to August, with most in July and early August. The first alatae appeared in the Rothamsted survey suction trap 0–34 days before aphids were found on the cereals, but during May and June no relationship was found between the numbers trapped and the number on the crop. Most species occurred first near the sheltered edge of the crop, but M. dirhodum was widespread over the field. Most infestations were quickly dispersed by the movements of older morphs; adults only stayed in one place for about 2 days. Alate M. dirhodum moved more often than apterae, but both morphs of S. avenae moved equally often and more frequently between larvipositions than did those of M. dirhodum. Apterae deposited more nymphs in a ‘group’ than alatae, and M. dirhodum deposited more than S. avenae. Few ‘groups’ persisted for more than a week. Although M. dirhodum occupied the crop area faster than S. avenae, all 0–3 m lengths of row sampled being infested within 2–5 wk of their first appearance, most or all of the tillers were colonized only in late July 1970.     

Focal adhesion kinase and beta1 integrin regulation of Na+, K+, 2Cl- cotransporter in osmosensing ion transporting cells of killifish, Fundulus heteroclitus

Focal adhesion kinase (FAK), also known as PYK2, is a tyrosine kinase that functions in integrin-mediated signaling in mechanosensitive cells but its role in osmosensing cells is unknown. Antibodies directed against phosphorylated FAK, whose epitopes are conserved among vertebrates, were used to follow phosphorylation patterns in an osmosensing ion secreting epithelium, the killifish (Fundulus heteroclitus) opercular membrane. At the electron microscopic level, a unique combination of integrin beta1, the phosphorylated form of FAK at tyrosine 407 (pY407) and Na(+), K(+), 2Cl(-) cotransporter (NKCC1) were all colocalized only on the basolateral membrane in chloride cells. The three proteins were also coimmunoprecipitated with each other in isotonic conditions, suggesting an osmosensing complex involving the three proteins. Only FAK pY407 was sensitive to hypotonic shock and became dephosphorylated with hypotonic shock, while FAK pY576 in the apical membrane and pY861 in cell-cell adhesions were insensitive to hypotonicity. NKCC1 contributes to NaCl secretion in seawater and previous reports showed that hypotonic shock (-60 mOsm/kg) rapidly inhibits Cl(-) secretion. These results indicate that chloride cells respond to hypotonic shock using integrin beta1 as an osmosensor that is connected to dephosphorylation of FAK pY407 which leads to NKCC1 deactivation in the basolateral membrane and the inhibition of NaCl secretion by these epithelial cells.     

Residency Duration and Shelter Quality Influence Vibratory Signalling Displays in A Territorial Caterpillar

Residents are more likely to win territorial disputes than intruders. One explanation for this prior resident advantage is that residents place a higher value on the resource and are therefore more motivated to win. Although value asymmetry models of animal contests often assume that contestants use information about resource value, information on the proximate cues affecting territorial behaviour is often lacking. We use a simple model system – territorial behaviour in the masked birch caterpillar (Drepana arcuata) to identify factors that affect territorial behaviour. Late instar caterpillars occupy solitary silken leaf shelters, which they defend against wandering conspecifics with a vibratory display. We evaluated how a caterpillar identifies itself as the owner and the factors that influence a resident's motivation to signal. To do so, we conducted three experiments between size‐matched residents and intruders to assess how residency duration and shelter quality independently affected territorial displays during the early stages of a contest. Experiment 1 (Time Exp.) demonstrated that resident signalling rates increase with increased duration on the leaf prior to introducing the intruder. Residents also signal more than intruders after residency periods of 1–3 min and longer, demonstrating that residents gather information about resource value shortly after occupying a leaf. Experiment 2 (Squatter Exp.) aimed to disentangle the effects of time on the leaf and silk accumulation. Squatters (individuals in a shelter made by another) placed for 1–3 min on a leaf containing a full silk shelter signalled more to intruders than did caterpillars placed on a fresh leaf for 1–3 min. Experiment 3 (Shelter Removal Exp.) showed that residents whose shelters had been removed signal less than those occupying an intact shelter, despite an equal length of time investing in them. Our experiment is the first to covary both prior residency duration and territory quality, and we find that the motivation of caterpillars to signal is a function of both of these attributes.