Phenology of Early-Season and Mid-Season Grasshoppers Shows Contrasted Responses Toward Climatic Variations in an Arid Area

Abstract

: The response of grasshoppers to climatic changes is rarely documented in arid areas. Here we address this subject in terms of phenology, i.e. the peaks of larva and adult abundance, according to species through bimonthly samplings in 2012 and 2013. The study was conducted in the Belezma National Park (northern Algeria) at Djerma (1021 m). The arid character is assessed by annual rainfalls around 330 mm. 2365 grasshoppers from 15 species were collected. Two assemblages were found, separated by the date of adult peaks, a spring one composed of 6 species (Pamphagidae and Pyrgomorphidae) and a summer one composed of 9 species (mainly Acrididae, Oedipodinae). Temperatures recorded in situ in 2102 were regularly higher than in 2013, almost from mid-May, whereas there was a humidity in spring 2012, and in summer 2013. In response to temperature and rainfall variations between these two years, the species of spring assemblage are in advance in 2012, and the contrary for those of summer assemblage. The phenology advance of spring assemblage species corresponds to a greater accumulation of degree-days during spring 2012. As regard summer assemblage, the 17 days-delay of nymphs observed in 2012 is reduced by 9 days in adults, in relation with the highest temperatures of summer 2012. Here it is hypothesized the major role of winter humidity that may have slowed down the hatching time of eggs and/or development of the first instars of summer assemblage species, surpassing the effect of temperatures. This winter humidity does not seem to affect the species of spring assemblage, mainly sensitive to warming.