Ocbil Theory as a Potential Unifying Framework for Investigating Narrow Endemism in Mediterranean Climate Regions

Abstract

OCBIL theory addresses the ecology, evolution, and conservation of biodiversity and cultural diversity on old climatically buffered infertile landscapes, which are especially prominent in southwest Australia and the Greater Cape Region of South Africa. Here, as a contribution to general theory on endemism, a few case studies are briefly discussed to ascertain the relevance of hypotheses in OCBIL theory to understanding narrow endemism in Mediterranean climate regions. Two new conservation management hypotheses are also introduced—minimising disturbance of OCBILS and conserving cross-culturally to achieve best outcomes. Case studies of endemics in southwest Australia (e.g., Eucalyptus caesia, Anigozanthos, Cephalotaceae, Daspypogonaceae) and South Africa (Moraea, Conophytum) and more limited evidence for the Mediterranean Region conform to OCBIL theory predictions. Narrow endemics, concentrated in OCBILs, have diverse origins that embrace major hypotheses of OCBIL theory such as prolonged persistence and diversification in refugia, limited dispersal, coping with inbreeding in small disjunct population systems (the James Effect), special adaptations to nutrient-deficient soils, and special vulnerabilities (e.g., to soil disturbance and removal). Minimising disturbance to OCBILs is recommended as the primary conservation strategy. OCBIL theory has a potentially significant role to play in advancing understanding of narrow endemism of plants in Mediterranean climate regions and elsewhere.

Abiotic correlates with diversity and distinctiveness in Sunshine Coast heathlands: Moisture, volcanic landscapes and patterned mounds

“…It is plausible that total richness is expected to increase with landscape age, as species accumulate through evolution and dispersal (Sarr et al, 2005). Communities on old, climatically buffered, infertile landscapes (OCBILs) display high species richness, endemism and distinctiveness (Hopper, 2009(Hopper, , 2023Yates et al, 2019). OCBILs are areas which have persisted for tens of millions of years, been subject to prolonged weathering and erosion, with no deposition or landscape rejuvenation through marine inundation or glaciation under a climate buffered from extremes by oceanic proximity (Hopper, 2009;Hopper et al, 2016).…”

“…As locations for protecting biota from the major impacts of anthropogenic climate change, it is crucial refugia are not lost through habitat modification or inappropriate management (Reside et al, 2014;Rossetto & Kooyman, 2021). OCBILs are possible refugia, occurring on climatically buffered and old landscapes with high numbers of endemics (Hopper, 2023). As well, Reside et al (2019) also advocate the identification and protection of 'refuges' which may be temporary or shifting, relieving species from stressors over shorter, spatial and ecological time scales.…”

“…OCBIL theory may well apply to the Tertiary and Triassic montane heaths of the Sunshine Coast, including the Glasshouse Mountains, and be in contrast to the heaths of the nearby coastal lowlands. Higher diversity could be expected in these areas and this would inform conservation planning including the management of disturbance and the value placed on even the small reserves (Hopper, 2023; Hopper et al., 2021).…”

“…As locations for protecting biota from the major impacts of anthropogenic climate change, it is crucial refugia are not lost through habitat modification or inappropriate management (Reside et al., 2014; Rossetto & Kooyman, 2021). OCBILs are possible refugia, occurring on climatically buffered and old landscapes with high numbers of endemics (Hopper, 2023). As well, Reside et al.…”

Plant diversity on the edge: floristics, phytogeography, fire responses, and plant conservation of Two Peoples Bay Nature Reserve in the context of OCBIL theory

“…Here, apart from testing key phytogeographic concepts regarding the transition from relatively high rainfall forests to semiarid woodlands and kwongkan, we also aimed to test OCBIL hypotheses (Hopper 2009(Hopper , 2018(Hopper , 2023Hopper et al 2016Hopper et al , 2021aSilveira et al 2021). OCBILs (an abbreviation for old, climatically-buffered, infertile landscapes) are identified by a combination of three attributes: old, persistent upland landscapes due to very slow denudation rates over millions of years, subdued disturbance regimes, most typically climatic buffering due to persistent proximity to oceans for 10s of millions of years; and geological quiescence and the absence of recent major events, such as glaciation, marine inundation, vulcanism, dust storms, and major bioturbation affecting soil rejuvenation.…”