Recruitment from seeds is among the most vulnerable stage for plants as global temperatures change. While germination is the means by which the vast majority of the world's flora regenerate naturally, a framework for accurately predicting which species are at greatest risk of germination failure during environmental perturbation is lacking. Taking a physiological approach, we assess how one family, the Cactaceae, may respond to global temperature change based on the thermal buffering capacity of the germination phenotype. We selected 55 cactus species from the Americas, all geo-referenced seed collections, reflecting the broad environmental envelope of the family across 70° of latitude and 3700 m of altitude. We then generated empirical data of the thermal germination response from which we estimated the minimum (T ), optimum (T ) and ceiling (T ) temperature for germination and the thermal time (θ ) for each species based on the linearity of germination rate with temperature. Species with the highest T and lowest T germinated fastest, and the interspecific sensitivity of the germination rate to temperature, as assessed through θ , varied tenfold. A left-skewed asymmetry in the germination rate with temperature was relatively common but the unimodal pattern typical of crop species failed for nearly half of the species due to insensitivity to temperature change at T . For 32 fully characterized species, seed thermal parameters correlated strongly with the mean temperature of the wettest quarter of the seed collection sites. By projecting the mean temperature of the wettest quarter under two climate change scenarios, we predict under the least conservative scenario (+3.7°C) that 25% of cactus species will have reduced germination performance, whilst the remainder will have an efficiency gain, by the end of the 21st century.
For a long time in situ conservation has been the main approach used to protect Chilean plant diversity. However, due to the high level of endemism of its flora (50%) and an increasing human impact on wild areas, ex situ conservation has become an urgent requirement to avoid the extinction of plant populations and species. Since 2001, the Instituto de Investigaciones Agropecuarias (INIA), Chile, has been working in partnership with the Royal Botanic Gardens Kew, (Kew) through the Millennium Seed Bank Project (MSB) with the objective of conserving 20% of the Chilean flora as seeds in long-term storage. This seed conservation effort has focussed mainly on the endangered and endemic plants of the Chilean drylands. Towards the end of the first phase of the MSB some 1482 seed collections representing 850 species and subspecies have been collected and safely preserved in the INIA Seed Base Bank and duplicated at Kew. Almost 70% of the total species collected are endemic to Chile and several of them are endangered. Additionally, seed germination research has been conducted for nearly 400 species and seed collections have been used to propagate several threatened species. Germination protocols have been published and disseminated online. Over 4,500 herbarium vouchers have been collected, largely duplicated at Kew and at the national herbarium in Chile. As a result of the inputs of INIA and the MSB, collaboration has been extended to other national stakeholders, mainly for plant taxonomy and seed collecting. In this context two training courses have been run for 70 staff/students. This training has contributed to the raising of general awareness of the need for the long-term protection of Chilean plant diversity and to demonstrate the key role that ex situ seed conservation can play in meeting this need.
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