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Modelled distributions and conservation status of the wild relatives of chile peppers

Crop wild relatives—the wild progenitors and closely related species to cultivated plants—have provided many important agronomic and nutritional traits for crop improvement (Dempewolf et al., 2017; Hajjar & Hodgkin, 2007). As populations of some of these taxa are adapted to extreme climates, adverse soil types, and important pests and diseases, they may provide key traits for the adaptation of crop plants to emerging and projected future challenges (Dempewolf et al., 2013).

Knowledge gaps with regard to wild genetic resources, including information on species’ taxonomy and relatedness to pertinent crops (i.e., gene pool assignments), geographic distributions, and values for traits of interest, constrain their potential use in plant breeding (Dempewolf et al., 2017; Miller & Khoury, 2018). Such knowledge gaps also affect conservation efforts, which are essential to protect vulnerable populations from habitat destruction, over‐harvesting, climate change, pollution, and invasive species (Bellon, Dulloo, Sardos, Thormann, & Burdon, 2017; Díaz et al., 2019; Jarvis, Lane, & Hijmans, 2008), and to ensure that these genetic resources are safeguarded for the long term and available for research in ex situ plant conservation repositories (Castañeda‐Álvarez et al., 2016; Gepts, 2006). Global analyses indicate that many crop wild relatives are poorly represented in gene banks (Castañeda‐Álvarez et al., 2016) and in protected areas (Khoury et al., 2019a). These reports highlight the urgency of addressing fundamental knowledge gaps to have the information available to guide conservation and crop improvement efforts.

The chile pepper genus (Capsicum L.) originated in the Andes Mountains, in north‐western South America, and subsequently diversified and dispersed, initially by birds and later also by people, throughout the neotropics and subtropics (Bosland & Votava, 2012; Carrizo Garcıa et al., 2016; Noss & Levey, 2014). There is evidence that humans were using wild chile peppers as early as 8,000–10,000 years ago (Davenport, 1970; Heiser, 1969; Pickersgill, 1966). Domesticated forms of chile peppers, as well as human dispersal of the fruits within the Americas, including to parts of the Caribbean, have been documented from at least 6,000 years ago (Jarrett et al., 2019; Perry et al., 2007; Perry & Flannery, 2017; Pickersgill, 1969, 1977; Walsh & Hoot, 2001). Originally used primarily for medicinal and ceremonial purposes, chile peppers became an important spice and vegetable for diverse Indigenous peoples (Bosland & Votava, 2012; Luna‐Ruiz, Nabhan, & Aguilar‐Meléndez, 2018; Smith, 1967).

Today, chile peppers are used worldwide as a vegetable, spice, colourant and pharmaceutical (Wall & Bosland, 1998). They are consumed daily by approximately a quarter of the world’s population (Halikowski Smith, 2015). Some chile pepper varieties have exceptionally high levels of provitamin A (Guzman, Bosland, & O’Connell, 2011; Kantar et al., 2016) and thus can make a significant contribution to fulfilling that nutritional requirement. Chile peppers are a high value crop (DeWitt & Bosland, 1993), providing economic benefits to both smallholder and larger‐scale farmers (Kahane et al., 2013).

Capsicum contains five principle domesticated chile pepper taxa—Capsicum annuum L. var. annuum, Capsicum baccatum L. var. pendulum (Willd.) Eshbaugh [incl. syn. Capsicum baccatum L. var. umbilicatum (Vell.) Hunz. & Barboza], Capsicum chinense Jacq., Capsicum frutescens L. and Capsicum pubescens Ruiz & Pav. (Bosland & Votava, 2012; Walsh & Hoot, 2001)—and ca. 37 wild taxa, some of which are also occasionally cultivated in home gardens (Table 1) (Baral & Bosland, 2002; Zonneveld et al., 2018). Among the domesticated species, C. annuum var. annuum is the most widely grown and studied. Both C. annuum var. annuum and C. baccatum var. pendulum have extant putative progenitors (Capsicum annuum var. glabriusculum (Dunal) Heiser & Pickersgill and C. baccatum L. var. baccatum, respectively); the progenitors of the remaining domesticates have not been identified.

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