An altitudinal transect as an indicator of responses of a spittlebug (Auchenorrhyncha: Cercopidae) to climate change

Abstract

A projected global temperature rise of 2-3°C can be represented by the change in mean annual temperature experienced over some 10° of latitude or approximately 700 m of altitude in the hills of northern Britain. Using an altitudinal rather than latitudinal transect has the advantage of allowing studies of population dynamics and adaptation of life cycles at the centre and edge of a species' range within the same locality with similar vegetation and photoperiod.Because of their unusual visibility in spittle masses, spittlebugs offer unusual opportunities to study population change in relation to environmental variables, including climate change.A population of spittlebugs, Neophilaenus lineatus (Auchenorrhyncha: Cercopidae) has been studied for 10 years on a transect from 20 m to 974 m on Ben Lomond, Scotland. The time lag in larval development corresponding with a 2-3°C shift in mean temperature is approximately 3 weeks. Much of this arises from a delay in hatching times. There is a significant relationship between the weather in March to July (which spans hatching and early larval development) and the maximum altitude at which larvae are found in the same year. The study suggests that insects with a similar life cycle to Neophilaenus lineatus will respond to a 2°C rise in mean temperature by extending their range and completing the life cycle two to three weeks earlier.