DIFFUSE TERMITINAE NESTS SHED LIGHT ON THE AFFINITIES OF LAETOLICHNUS KWEKAI (KRAUSICHNIDAE)

ABSTRACT The insect trace fossil Laetolichnus kwekai, which is composed of a small chamber extending to slender cylinders at each end, was tentatively included in the ichnofamily Krausichnidae as termite nests. New evidence presented here provides information to validate these inferences. A more complex structure formed by interconnected Laetolichnus was recently found in the same Pliocene deposits (Laetoli, Tanzania) as the isolated specimens reported previously. Our study confirms inclusion of Laetolichnus in Krausichnidae and supports the inference that it represents a nest of a social insect. Neoichnological field studies in the coastal dunes of Buenos Aires Province, Argentina, were undertaken to refine further the nature of these affinities. Survey of the dune surface revealed abundant loose fragments of termite nests of a size and shape comparable to that of L. kwekai. The fragile nests constructed by Onkotermes brevicorniger, which are described here in detail for the first time, enable us to interpret the fossil structures. They consist of connected chambers similar to the interconnected Laetolichnus. These were frequently exposed and broken by wind action resulting in loose fragments similar to the isolated Laetolichnus. The Celliforma ichnofacies represented at Laetoli, which contains L. kwekai, indicates arid or semiarid shrublands and woodlands. The distribution of O. brevicorniger also corresponds to arid and semiarid shrublands and dry woodlands of Argentina. Although the African termite producer of L. kwekai and the South American Onkotermes would be phylogenetically unrelated, the analogous structures probably reflect convergent nesting behaviors as an adaptation to similar arid to semiarid environmental conditions.

Abscisic acid and its metabolites are involved in drought tolerance in four native species of Patagonian semiarid shrublands (Argentina)

Drought is the main stress that affects growth of native species of Patagonian Monte. Physiological and biochemical traits with functional roles in adaptation to drought are still scarce in native species. The aim of this study was to evaluate changes in dry matter content and abscisic acid (ABA) and its metabolites (phaseic acid-PA, dihydrophaseic acid-DPA, ABA conjugated with glucose-ABA-GE) level in green leaves and fine roots of four native species during contrasting seasons regarding water availability. Results show that grasses had higher leaf dry matter content (LDMC) and root dry matter content (RDMC) than Lycium chilense shrub and LDMC decreased during autumn in Larrea divaricata. In green leaves, there was an interaction between species and seasons for ABA and PA contents. L. divaricata had high ABA content during spring and low ABA content during autumn; while L. chilense showed the opposite pattern. During spring, drought tolerant species had high PA content while drought avoidant species had low PA content, and during autumn these species showed the opposite pattern. ABA-GE content was highest in L. chilense green leaves. In fine roots, ABA content was highest in L. divaricata and during spring PA was higher in L. divaricata than P. ligularis and L. chilense. PA was the only metabolite that decreased in L. divaricata during autumn. Results showed that ABA homeostasis maintains the functioning of different life forms with different drought resistance strategies in Patagonia semiarid shrublands. In green leaves of the drought avoidant L. chilense shrub, the ABA conjugation pathway was active in both seasons. During spring, the most drought tolerant L. divaricata showed highest activation of ABA synthesis and ABA oxidation pathways. During autumn L. chilense showed highest activation of ABA synthesis and together with P. ligularis showed active the ABA oxidation pathway.

An isolated population of the southern scrub-robin (Drymodes brunneopygia) in the Great Victoria Desert

From 2013 to 2015 we recorded an isolated, highly fragmented and previously undocumented population of the southern scrub-robin within the arid shrublands of the Great Victoria Desert. In this region, the southern scrub-robin persists in scattered and intermittent areas of long-unburnt mulga (Acacia spp.) shrubland, with a dense shrubby understorey dominated by Aluta maisonneuvei and Eremophila shrubs. The Great Victoria Desert supports the only known desert population as the southern scrub-robin otherwise occurs in the temperate and semiarid shrublands of southern Australia and occurs in the desert at the arid extreme of its range. Fire is highlighted as a significant threatening process due to the species’ restricted occurrence (less than 5% of the landscape in the region), low reproductive rate, limited dispersal capability and persistence within long-unburnt and fire-sensitive habitats. As forecast environmental changes are likely to render the arid extremes of the species’ range unsuitable, this outlying, desert population is potentially declining and of conservation significance.