Diversity and distribution of the last remnants of endemic juniper woodlands on Tenerife, Canary Islands

Abstract

Identifying ecological requirements, species diversity patterns and distribution ranges of habitats of interest is an important task when developing conservation and restoration programs. The Canarian juniper woodland formed by Juniperus turbinata ssp. canariensis is listed as a priority habitat by the European Union. Although very common in the past, this vegetation type has suffered immense destruction and degradation over the last five centuries on the Canary Islands, especially on the largest most populated island of Tenerife. We evaluated the geographical distribution range of the last remnants of Canarian juniper woodlands on Tenerife and analyzed their ecological status, floristic composition and plant species diversity. Despite the degradation of the original vegetation, we still observed outstanding species diversity. Endemic species richness and number of typical habitat species were best predicted by summer rainfall, which seems to be the limiting factor for this habitat in the lower drier regions. Human disturbance has had a negative effect on endemic species richness but a positive effect on the distribution of alien plants, highlighting the potential threat to this habitat. Ecological characterization and floristic composition were most influenced by climatic factors related to the dichotomy of a humid windward and a drier leeward slope of the island and by altitude. However, vegetation structure and human disturbance also determined species composition. Environmental requirements indicated a circuminsular potential distribution of this habitat. Given the exceptional plant diversity, the scarcity of dense stands and the low protection status, immediate protection of the remaining stands and future restoration programs should be the priority for conservation strategies of this endemic vegetation type.

Influence of natural habitat fragmentation on the genetic structure of Canarian populations of Juniperus turbinata

“…Regardless of whether Macaronesian populations represent a well-defined subspecies, they are scarce and threatened, and the islands where they occur are largely considered priority natural habitats by the European Directive 92/43, due to the particular richness of endemic species (Otto et al 2012). At present, Canarian populations of J. turbinata are located in the five westernmost islands of the archipelago, and only occupy some 10% of the species potential distribution range due to widespread human disturbance (Fernández-Palacios et al 2008;Del Arco et al 2010).…”

“…Although there are several studies that point out the dynamics of Canarian populations of J. turbinata (Fernández-Palacios et al 2008;Otto et al 2012), there is a lack of knowledge on the genetic structure of these populations. As such, research into the amount and distribution of genetic diversity is required to a better understanding of associated ecological processes such as island colonization, gene flow among populations or historical bottlenecks, and to enhance and inform existing conservation measures aimed at protecting the populations (Fernández-Palacios et al 2008;Otto et al 2010).…”

Past, present, and future geographic range of the relict Mediterranean and Macaronesian Juniperus phoenicea complex

“…It does not grow on the driest Canary Islands, Lanzarote, and Fuerteventura, which are exposed to dry and warm winds (Bechtel, 2016;Cropper, 2013). The climate of the Canary Islands is oceanic, with low temperature amplitudes and high humidity, but J. canariensis forms homogeneous patches and enters shrub communities in places with relatively low rainfall (Fernández-Palacios et al, 2008Luis González et al, 2017;Otto et al, 2010Otto et al, , 2012Romo 2018;Romo et al, 2014;Romo & Salvà-Catarineu, 2013). It grows at elevations mostly between 400 and 1,000 m, higher on the leeward than the windward sides of the islands (Fernández-Palacios et al, 2008;Otto et al, 2012).…”

“…Mediterranean and Macaronesian regions are important biodiversity hotspots at the global scale. However, they have been greatly modified by human activity for millennia and they are vulnerable to current and future climate change (Otto et al, 2012;Thompson, 2005).…”

A reappraisal of the role of humans in the biotic disturbance of islands

“…Low- to mid-level elevations can shelter the largest proportion of an island's endemicity (Otto et al 2007, 2012), and hence are susceptible to heavier biodiversity losses from human settlement. Steinbauer et al (2012) found that the percentage of single island endemics was higher in the mid-elevation thermophilous scrub, the most negatively affected vegetation belt in the Canary Islands (Otto et al 2012). However, the Canarian lowlands, especially on leeward slopes, are even more profoundly affected by urbanization and infrastructure.…”