Steep topography buffers threatened gymnosperm species against anthropogenic pressures in China

Spatial heterogeneity of extinction risk for flowering plants in China

Understanding the variability of extinction risk and its potential drivers across different spatial extents is crucial to revealing the underlying processes of biodiversity loss and sustainability. However, in countries with high climatic and topographic heterogeneity, studies on extinction risk are often challenged by complexities associated with extent effects. Here, using 2.02 million fine-grained distribution records and a phylogeny including 27,185 species, we find that the extinction risk of flowering plants in China is spatially concentrated in southwestern China. Our analyses suggest that spatial extinction risks of flowering plants in China may be caused by multiple drivers and are extent dependent. Vegetation structure based on proportion of growth forms is likely the dominant extinction driver at the national extent, followed by climatic and evolutionary drivers. Finer extent analyses indicate that the potential dominant extinction drivers vary across zones and vegetation regions. Despite regional heterogeneity, we detect a geographical continuity potential in extinction drivers, with variation in West China dominated by vegetation structure, South China by climate, and North China by evolution. Our findings highlight that identification of potential extent-dependent drivers of extinction risk is crucial for targeted conservation practice in countries like China.

Half of global islands have reached critical area thresholds for undergoing rapid increases in biological invasions

Biological invasions are among the threats to global biodiversity and social sustainability, especially on islands. Identifying the threshold of area at which non-native species begin to increase abruptly is crucial for early prevention strategies. The small-island effect (SIE) was proposed to quantify the nonlinear relationship between native species richness and area but has not yet been applied to non-native species and thus to predict the key breakpoints at which established non-native species start to increase rapidly. Based on an extensive global dataset, including 769 species of non-native birds, mammals, amphibians and reptiles established on 4277 islands across 54 archipelagos, we detected a high prevalence of SIEs across 66.7% of archipelagos. Approximately 50% of islands have reached the threshold area and thus may be undergoing a rapid increase in biological invasions. SIEs were more likely to occur in those archipelagos with more non-native species introduction events, more established historical non-native species, lower habitat diversity and larger archipelago area range. Our findings may have important implications not only for targeted surveillance of biological invasions on global islands but also for predicting the responses of both non-native and native species to ongoing habitat fragmentation under sustained land-use modification and climate change.

Biotic Threats to Cycas micronesica Continue to Expand to Complicate Conservation Decisions

Simple Summary

Effective conservation of endangered plant species requires identifying their greatest threats to formulate management protocols. Invasive species are a result of global change and are a major threat to biodiversity. We used the island cycad Cycas micronesica K.D. Hill as a model that represents the global issues of conservation science and invasion biology. In Guam, several non-native insect invasions began in 2003 and have combined to threaten the island population of this cycad species. In this article, we summarize the history of reported invasions and the reported non-native insect herbivores that have recently increased the threat status. We also discuss the interactions among herbivores that threaten the sustainability of C. micronesica on the island of Guam.

Abstract

Invasions of non-native species can threaten native biodiversity, and island ecosystems are ideal for studying these phenomena. In this article, first, we report on the invasive species that combine to threaten the island cycad Cycas micronesica by reviewing the history of previously reported invasions and providing an update of recent invasions. Then, we prioritize the threat status of each herbivore and the interactions among them. Plant damage was initiated in 2003─2005 by the non-native Aulacaspis yasumatsui Takagi armored scale, Erechthias sp. Meyrick leaf miner, and Luthrodes pandava Horsfield butterfly, which elicited unprecedented irruptions of the native Acalolepta marianarum Aurivillius stem borer and increased herbivory by feral pigs (Sus scrofa L.). The combined impact of these five consumers represents the greatest sustained threat to the cycad tree species. Mitigation of the damage caused by phytophagous non-native species is urgently needed to conserve this unique gymnosperm tree.

The potential impact of future climate on the distribution of European yew (Taxus baccata L.) in the Hyrcanian Forest region (Iran)

The Hyrcanian Forest region is rich in relict species, and endemic and endangered species. Although there are concerns about climate change, its influence on tree species in the Hyrcanian forests in the north of Iran is still unidentified. Taxus baccata is among the few conifer species found in the region, and the present study aims to evaluate the potential impact of climate change on the distribution of T. baccata. For this purpose, we used ensemble species distribution modeling with ten algorithms and based on two geographic extents (global and regional) and climate data for different climate change scenarios. For the regional extent, we calibrated the models in Hyrcanian forests including the three provinces in the north of Iran. For the global extent, we calibrated the models on the whole range distribution of T. baccata. In both cases, we applied the models to predict the distribution of T. baccata in northern Iran under current, 2050, and 2070 climates. In regional extent modeling, precipitation of coldest quarter and in global extent modeling temperature seasonality emerged as the most important variables. Present environmental suitability estimates indicated that the suitable area for T. baccata in Hyrcanian forests is 5.89 × 10³ km² (regional modeling) to 9.74 × 10³ km² (global modeling). The modeling suggests that climate change under representative concentration pathways (RCP) 8.5 is likely to lead to strong suitability reductions in the region, with just between 0.63 × 10³ km² (regional modeling) and 0.57 × 10³ km² (global modeling) suitable area in 2070. Hence, T. baccata risks losing most currently suitable areas in the Hyrcanian forests under climate change. The results of the present study suggest there should be focus on conservation of areas predicted to remain suitable through near-future climate change and provide an estimate of the availability of suitable areas for the regeneration of T. baccata and its use in reforestation.