Two spellings of the species name (latastei and latasti) appeared in different places in the original description by Boscá, and were subsequently used as the valid name by different authors. The validity of both names was in dispute for several years (see Brito 2017) until 2017, when the International Commission for Zoological Nomenclature accepted latastei as the name with priority (ICZN 2017).

A recent taxonomic revision - combining genetic, morphological and ecological data - restricted Vipera latastei to the Iberian Peninsula and defined it as comprising three extant (V. latastei latastei, V. latastei gaditana and V. latastei arundana) and one extinct (V. latastei ebusitana) subspecies (Martínez-Freiría et al. 2021, Torres-Roig et al. 2021). Populations from North Africa, previously included within V. l. gaditana, are currently assigned to the phylogenetically sister species Vipera monticola following Martínez-Freiría et al. (2021).

This species is endemic to the Iberian Peninsula, where it is widespread but with occurrence limited in part by human activity, and it is likely to have once occurred more widely in the Iberian lowlands. Data collected between 1980 and 2017 suggest that the species declined by 34.2% across its range over a three-generation period estimated as 27 years, driven primarily by habitat conversion and degradation with secondary impacts from persecution. Declines are likely to be ongoing at a comparable rate, as the causes of the decline have not ceased, and long-term climate projections suggest that it may lose much of its potential distribution - largely limited to montane habitats in protected areas - by 2070. It is consequently assessed as Vulnerable (VU A2c) both globally and for the European Union, which encompasses its entire distribution.

This species is endemic to Europe where it is widespread in Portugal and Spain (Martínez-Freiría et al. 2021). It occurs throughout the entirety of mainland Portugal, although extant subpopulations in this country are scattered, isolated and generally restricted to montane areas (Brito 2008, 2017, Martínez-Freiría et al. 2014). In Spain, its northern range limit is along the southern slopes of the Cantabrian Mountains and Pyrenees (Pleguezuelos and Santos 2022, Martínez-Freiría et al. 2014, 2021, Brito 2017). Its area of occupancy was probably wider in the past but is now limited by the degradation of natural habitats (Martínez-Freiría et al. 2014, 2021, Brito 2017, Santos et al. 2006). It is absent from islands: the only known island subpopulation, on the Columbretes Islands off the east coast of mainland Spain, was lost in the mid-19^th Century (Bernis 1968).

The species occurs as three mtDNA lineages: both the western and eastern lineages are widespread and essentially continuously distributed across the Iberian Central System and Sierra Morena (Martínez-Freiría et al. 2021). The southern lineage (described as the subspecies Vipera latastei arundana) has a relatively small range in southern Spain (Serranía de Ronda and its immediate surroundings), which appears to be isolated from the western lineage (recognized as the subspecies V. l. gaditana) by the Guadalquivir River basin, but exhibits a narrow contact zone with the eastern clade (Martínez-Freiría et al. 2021).

Subfossil remains from Ibiza indicate that it once occurred in the Balearic Islands, and it is believed to have become extinct on Ibiza shortly after human colonisation of the island (Torres-Roig et al. 2021). The species occurs from sea level up to almost 2,800 m asl, but more usually between 500-1,500 m asl (Martínez-Freiría et al. 2021). This may be a consequence of land transformation in lowland areas, where it generally occurs in areas with limited disturbance (Santos et al. 2006).

Throughout its range, the population occurs as dispersed, isolated subpopulations that occur in moderate or low densities, although it "seems to be frequent" in the Gerês Mountains in Portugal (Brito 2017) and other northern regions of Spain, such as the provinces of Burgos and Soria (F. Martínez-Freiría pers. comm. 2023). Subpopulations are generally restricted to mountain ranges (Pleguezuelos and Santos 2002, Brito 2008, Martínez-Freiría et al. 2014, Brito 2017). It is hypothesised that this is largely a consequence of habitat modification at lower elevations rather than a natural preference for montane habitats, an inference supported by the persistence of extant subpopulations in lowland areas with low human population densities (Santos et al. 2006).

A population monitoring study in the Gerês Mountains in northern Portugal over four years recorded densities of 3.3-5.2 vipers /ha (mean 4.4), with a stable trend over this period (Brito 2003). The only other subpopulation for which quantitative data are available, the Sedano Valley in north-central Spain, recorded approximately two individuals per 2 km of line transects (Martínez-Freiría et al. 2010).

In the centre and south of the range sightings are scarce and anecdotal despite considerable survey effort targeted at snakes (e.g. Santos et al. 2007). Consequently, no quantitative data are available on population trends, but this suggests population densities are low throughout this region (F. Martínez-Freiría pers. comm. 2022).

The Cadiz subpopulation (now recognised as the subspecies V. l. arundana) was recognised to be isolated, fragmentary and occurring in low densities as early as the early 1970s (Busack 1977). At least one local extinction has been recorded in lowland Cadiz, with anecdotal evidence of a decline in another (Pleguezuelos et al. 2016).

The species is believed to have declined historically through much of the Iberian lowlands, and to a lesser extent in some montane areas (Brito 2017, Martínez-Freiría et al. 2014, Pleguezuelos et al. 2016). The low proportion of recent records among compiled atlas data (at the scale of UTM 10x10 km grid cells) implies that this decline will likely continue (Brito 2017). A subsequent study modelling rates of decline based on citizen science data collected between 1980 and 2017 found that the population had declined by 48.1% in Spain over this period (Santos et al. 2022). Santos et al. (2022, table 1) infer a decline of 22.8% over 18 years, which they regarded as corresponding to a three-generation period. F. Martínez-Freiría (pers. comm. 2022) estimates, based on reproductive frequencies and demographic data available from the two studied northern subpopulations (see attached Supplementary Material), that the generation length is likely to be as long as 8.5-9.5 (median 9) years, in which case the rate of decline derived by Santos et al. (2022) may exceed 30% in three generations (34.2% over 27 years). The latter figure is accepted here.

This viper is restricted to Mediterranean climates and generally prefers saxicolous habitats in steep slopes, occupies dry rocky areas frequently covered by bushes, stone walls with some vegetation that separate crop fields and pastures, and even rock outcrops in the edges of intensive agriculture fields in its north-central range. It appears tolerant of topographical and climatic variability across most of the Iberian Peninsula, but its realised niche is likely to be restricted by the impacts of human activities and competition with related species (Brito 2017, Chamorro et al. 2021, Martínez-Freiría et al. 2014, Santos et al. 2006). It is also present in open areas of oaks, conifers and mixed forests that contain favourable sites for refuge, thermoregulation and hibernation. It can also occasionally be present in sandy coastal pine forests and in sandy areas with shrubby vegetation, such as the coastal dunes of the Doñana National Park (Brito 2017, Martínez-Freiría et al. 2014, 2021). Conversely in southern parts of its range, the snake shows rather low habitat diversity, occurring in the least diverse range of habitats of any snake other than the smooth snake in Andalusia (Segura et al. 2007).

Although it occurs across varied habitat types, within these it is reliant on areas with a combination of suitable refugia, hibernacula, and sites that permit thermoregulation (Brito 2017). Radio-tracking in the Gerês Mountains in northern Portugal found that the most-used habitat was open woodland (including heavily logged areas) with thickets, which it preferred to pure thicket (Brito 2017). Its habitat use varies seasonally, but in all seasons relies on the presence of vegetation cover, logs or rocks, and as it actively searches for different types of habitat in different seasons it is tied to areas with suitably diverse structural elements (Brito 2017).

The nominate form has principally been recorded in areas with annual precipitation below 790 mm, however, other subspecies have been found in moderate or high levels of precipitation (up to 2,200 mm) (Martínez-Freiría et al. 2021). The females give birth to up to 13 young (Geniez 2018). This author suggested that typical litter sizes are 2-6, however, this is based on opportunistic reports (F. Martínez-Freiría pers. comm. 2023). Data from a total of 22 reproductive females (Martínez-Freiría et al. 2010, F. Martínez-Freiría pers. comm. 2023) found litter sizes of 3-12 (mean 7.45, mode 7). On average females give birth only once every three years based on data available for the entire Iberian Peninsula (Pleguezuelos et al. 2007), although data from several sites suggests that in some areas it may breed at least as frequently as once every two years (summarised by Brito 2017). Sexual maturity is reached at 4 (males) and 5 (female) years of age in northern Portugal (Brito 2017). The maximum recorded longevity is 11 years in males and 14 in females (Brito and Rebelo 2003).

This has been identified as the most threatened snake in Iberia as a result of its ecological specialisation, low reproductive potential and the impacts of habitat destruction (Santos et al. 2007, Santos 2011). Busack et al. (1977) hypothesised that the scarcity and fragmentary distribution of this species in lowland areas of Cadiz was a consequence of centuries of goat grazing and agricultural development. At one large cattle grazing site with remnant native vegetation, the managing shepherd reported that viper bites on livestock had declined in the 35 years prior to 2012 (Pleguezuelos et al. 2016). Over this time period, the area of the site had declined by about a sixth as a result of agricultural development (Pleguezuelos et al. 2016). No vipers were recorded in surveys of this site in 2012 and 2013, however, this species is elusive and can be difficult to detect (Pleguezuelos et al. 2016, Speybroeck et al. 2016).

Although the snake can occupy a range of agricultural habitats (e.g. in north-central Spain - Zuazo et al. 2019), it exhibits a preference for areas without competing species and exhibits a negative relationship with the asp viper (Vipera aspis) and Seoane's viper (Vipera seoanei) in contact zones (Martínez-Freiría 2009; Martínez-Freiría et al. 2008, Brito 2017, Chamorro et al. 2021). It may therefore be absent from areas where land transformation favours the asp viper or other competing vipers (Chamorro et al. 2021). This species' reliance on specific habitat structure both restricts its dispersal capacity and makes it highly sensitive to even partial degradation of its habitat, making subpopulations highly susceptible to fragmentation (Brito 2017). Intensive farming, which is associated with the clearance of forest, bushes and stone walls that provide important shelter and shade-providing resources, is a particular threat as it homogenizes the previously diverse mosaic habitat mosaic on which this snake depends (Brito 2017). A widespread, intensive wheat-producing campaign from the 1930s cleared vast areas of Alentejo in Portugal, and is regarded as a significant contributor to population fragmentation in Lataste's Viper (Brito 2017).

Wildfire has a major impact on Mediterranean systems due to the ongoing modification of the fire regime towards more intense, frequent, and larger wildfires. This trend is continuing due to rural abandonment and fire suppression policies which increase fuel load, reduce landscape openness, and can produce catastrophic summer megafire seasons. This dynamic is threatening viper populations, especially in fire-prone regions from the Iberian Peninsula. Fire has been implicated as one of the main factors driving a decline in this species in Catalonia (Parellada 1995). A comparison of burned and unburned sites in the western Mediterranean found that the snake was detected more often in unburned than recently burned patches (X. Santos, unpublished data)

Intensive forestry clears native forests and replaces them with exotic pine and eucalyptus (Brito 2017). The associated soil acidification resulting from planting with fast-growing trees is hypothesized to affect invertebrate communities and so the food chain on which the snake ultimately relies, while canopy closure from dense plantations hinders thermoregulation (Langton and Burton 1997). Such plantations have replaced "extensive areas of favourable habitat" for this snake in Galicia and in north and central Portugal (Brito 2017).

Urban development and associated highway construction have fragmented extensive areas of Catalonia and the Atlantic coast of Portugal (Brito 2017). There may be some impact from road mortality: while any population-level impacts cannot be quantified this is one of the most commonly recorded snakes as roadkill in northern Portugal and Spain (Martínez-Freiría and Brito 2012).

The species is widely persecuted, and the only known insular subpopulation was lost within three years in the mid-19th Century during lighthouse construction, in which more than 2,700 individuals were killed (Brito 2017).

Climate modelling projects declines of between 74 and 78% of this species' potential distribution between 2040 and 2070 (Araújo et al. 2011). Climate-driven droughts and temperature increases are expected to strongly impact habitats of this species, promoting local extinction of southern Iberian subpopulations.

The species is medically important according to the World Health Organisation, and the collection of venom for research and the development of antivenoms is required (Avella et al. 2022).

The species is marginally utilised for the traditional creation of amulets, a practice that appears to date to the Middle Ages (Nobre 1928). Collection for this purpose is mainly restricted to the north of Portugal (Maia 1960) although associated trade occurs country-wide, and advertisements for viper-head amulets suggest that it may have entered international trade (Brito 2017).

Trade in vipers as pets is common in Europe, but there is little information on whether this species is traded as a pet to any significant degree (F. Martínez-Freiría pers. comm. 2022).

This species is listed in Appendix II of the Bern Convention and is protected by national legislation in Portugal and Spain. Most records of the species occur in protected areas across Portugal and Spain. Restoration and protection of suitable habitats, resources and natural processes is recommended (F. Martínez-Freiría pers. comm. 2022). Population monitoring is needed to clarify rates of decline, and a conservation plan should be developed (F. Martínez-Freiría pers. comm. 2022). There is an important need for formal education, awareness and communications regarding this and other snake species to emphasise their ecological role, and to reduce both human persecution and the traditional exploitation of this species.