Supply-side biogeography: geographic patterns of settlement and early mortality for a barnacle approaching its range limit

Abstract

Species range limits are often associated with reduced adult densities, and this may reflect the failure of a particular life-history stage. For benthic marine invertebrates, settlement is a time of great mortality that strongly influences adult population structure, at least at local spatial scales. In south-eastern Australia we determined that adult abundance of the intertidal barnacle Tesseropora rosea declines over a 450 km region of rocky shore from the middle to the southern limit of its range, and we tested the hypothesis that this biogeographic pattern reflects variations in the production, settlement, or early post-settlement mortality of larvae or adult mortality. Sampling at 2 sites on 11 rocky shores in this region over 2 yr revealed that none of the life-history stages or demographic processes displayed a latitudinal gradient or a clear decline towards the south, and settlement and adult mortality were highly variable among locations. Indeed local variation in early lifehistory processes and adult mortality appears to dictate regional variability and observed latitudinal patterns of adult abundance of T. rosea, but longer term studies spanning at least a decade may determine if storage from one strong year in recruitment can set patterns of adult abundance.KEY WORDS: Abundant-centre hypothesis · Early post-settlement mortality · Tesseropora rosea · Adult mortality · Geographic distribution · Latitudinal gradient Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 412: [141][142][143][144][145][146][147][148][149][150] 2010 although these supply-side processes are often highly variable in space and time (see Underwood & Fairweather 1989, Caley et al. 1996, Hunt & Scheibling 1997, they sometimes reflect latitudinal gradients of temperature, currents, wave exposure and nutrient availability in the ocean (Connolly & Roughgarden 1998, Connolly et al. 2001, Zacherl et al. 2003, Sanford et al. 2006. Consequently, the geographic distribution of benthic marine invertebrates, particularly as a species approaches its range limit, may be strongly influenced by latitudinal gradients in the supply and early life history of larvae. Alternatively, processes operating at more local scales in the post-recruitment environment (e.g. storm events, habitat, microclimates, predation) could override larger scale patterns of recruitment that might determine geographic patterns in adult abundance (Helmuth 1998). Measuring settlement and early post-settlement mortality of benthic marine invertebrates is often difficult, however, because larvae are small and often die soon after settlement. Few studies have measured these early lifehistory processes simultaneously across large geographic scales (but see Caffey 1985, Connolly et al. 2001, Hughes et al. 2002, but such studies can yield important insights into the processes setting the range limits of species.Along the linear coastline of south-eastern Australia, there is great potential for the population size of sessile...

Manipulating thermal stress on rocky shores to predict patterns of recruitment of marine invertebrates under a changing climate

“…Our previous work confirms that T. rosea populations at Garie Beach typically experience high rates of early post-settlement survival (~50%) in comparison to other populations along the southeast coast of Australia (0 to 20%) (see Lathlean et al 2010). However, this does not explain why we found no difference in early post-settlement survival among our 3 differently coloured plates.…”

“…East to southeasterly waves are the most common and occur year round, with easterly waves peaking in March and November and southeasterly waves peaking in May and November (Short & Trenaman 1992). T. rosea on this headland is abundant, and populations have been continuously monitored over the past 5 yr (Hidas et al 2010, Lathlean et al 2010. We have observed a distinct breeding and settlement period between January and June each year with larvae usually arriving in 3 distinct pulses, once in January, then from late February to early April and then again in May (Denley & Underwood 1979, Lathlean et al 2010).…”

Rocky intertidal temperature variability along the southeast coast of Australia: comparing data from in situ loggers, satellite-derived SST and terrestrial weather stations

“…These southward-flowing warm-core eddies produce latitudinal temperature gradients and are expected to increase in strength, penetrating further south, under future climate change scenarios (Roughan & Middleton 2004, Lough 2009, Ridgway & Hill 2009). Many species have their northern or southern geographical range limits within this region (Knox 1963, O'Hara & Poore 2000, Hidas et al 2007, 2010, see also Ayre et al 2009, Lathlean et al 2010, and therefore, we might expect many of these species' range limits to shift with response to climate change. However, there is a significant gap in our understanding of the typical spatial and temporal temperature regimes experienced by intertidal organisms along the southeast coast of Australia, and researchers in the past have simply used satellite-or buoy-derived SST as a measure of large-scale temperature variability.…”

Temperature variability at the larval scale affects early survival and growth of an intertidal barnacle

“…We focussed our study on the dominant, habitat-forming barnacle Tesseropora rosea which is highly abundant in the mid shore area on exposed rocky shores within this region (Hidas et al 2010, Lathlean et al 2010. Tesseropora rosea has a largely distinct breeding and settlement period, which is well suited to investigating factors affecting early life history processes.…”