Extraordinary concentrations of local endemism associated with arid-land springs

Abstract

Introduction: While the biodiversity value of springs is recognised, it has not been systematically compiled. The aim of the current study is to highlight the extraordinary endemism associated with the isolated habitat of arid-land springs at three locations in two continents.Methods: The habitat endemism of the eukaryote species associated with the aquatic and terrestrial habitats at Ash Meadows in the USA, Byarri in Australia and Cuatro Ciénegas in Mexico was assembled based on their geographic distribution.Results: The currently-known aquatic and semi-aquatic endemic species number 27 at Ash Meadows, 31 at Byarri and 34 at Cuatro Ciénegas. Terrestrial endemic species are represented by two species at Ash Meadows, five at Byarri and 26 at Cuatro Ciénegas. The terrestrial endemics are associated with the scalded areas surrounding the springs impregnated with soda and gypsum. The persistence of the endemics is astonishing given that the wetlands represent tiny islands of habitat (216 small wetlands over 40 km2 in the case of Byarri).Discussion: A key factor for the persistence and radiation of endemic species is the stability and permanence of the wetlands over evolutionary time-scales. Genetic evidence indicates the presence of both paleo-endemics, species that persisted in spring wetlands as relics of previous mesic climates; and neo-endemics that have dispersed from more mesic environments and subsequently radiated in the spring wetlands as distinct forms. The former evolved from their relatives greater than 106 ya and the latter less than 106 ya. The concentration of endemic species in and around arid-land springs is among the highest concentrations of endemic organisms specialised to a particular habitat and substantiates the paramount conservation significance of desert springs.

The Cultural Ecohydrogeology of Mediterranean-Climate Springs: A Global Review with Case Studies

“…In contrast, many California springs and those in other desert regions support high numbers of endemic invertebrate and fish species (e.g., [56]). Phenes raptor (Odonata: Petaluridae) (Figure 40) is one of only 10 species remaining in this oldest, most ancestral lineage of dragonflies.…”

“…We suggest that isolation, water quality, persistence, and biogeography shape spring ecosystem structure and function, while climate, water quality, size, and productivity influence cultural appropriation and, reciprocally, cultural evolution. Collectively, these physical, ecological, and socio-cultural interactions help explain both the high levels of biodiversity and endemism at Mediterranean springs, and the intensity of human use and development [56,281,282].…”

“…Studies of the Eel River in California by Power et al [54] corroborated those patterns, adding the characteristic of seasonal variability in productivity. Seasonal aridity can also reduce and disrupt habitat connectivity, and upland aridity can result in patterns of isolation that may increase the evolution of endemism in streams [54,55] and in springs (e.g., [56]). In contrast, Montezuma Well springs in the small MCZ strip mapped in central Arizona emerges from a 13,300-year flow path with constant temperature and with naturally high concentrations of calcium carbonate and arsenic-rich water [57,58].…”

Mediterranean springs: Keystone ecosystems and biodiversity refugia threatened by global change

“…The characteristics of these regions make their springs, and spring ecosystems, of paramount importance for human development and biodiversity conservation. Spring ecosystems from these regions (hereafter, Mediterranean spring ecosystems) have been described as refugia for a wide array of organisms, including a large number of endemic species found only in one single spring (Fensham, Ponder, et al, 2023;Freyhof et al, 2017).…”

“…The characteristics of these regions make their springs, and spring ecosystems, of paramount importance for human development and biodiversity conservation. Spring ecosystems from these regions (hereafter, Mediterranean spring ecosystems) have been described as refugia for a wide array of organisms, including a large number of endemic species found only in one single spring (Fensham, Ponder, et al., 2023; Freyhof et al., 2017). Spring ecosystems have been reported to support high values of both freshwater (Bes et al., 2018; Cantonati, Füreder, et al., 2012; Fernández‐Martínez et al., 2021; Sabatino et al., 2003) and terrestrial biodiversity (Votto et al., 2020; Zamora‐Marín, Zamora‐López, et al., 2021).…”