Boundaries

This ecoregion extends across the southernmost part of Spain, from the mouth of the Guadiana River in the west to the mouth of the Segura River in the east. It encompasses the drainage basins of the Guadiana, Guadalquivir, Segura, and other coastal rivers. This ecoregion is bordered to the south by the Atlantic Ocean and Mediterranean Sea and to the north by the Montes de Toledo.

Topography

The topography of this ecoregion is varied and ranges from plains and gentle hills in the Guadalquivir basin to the massifs, mountains and valleys of the Bethic Cordillera and Meseta Central. The upper catchment of the Guadiana River also drains the Meseta Central, which is a high plateau that slopes westward. Mountain ranges within the Bethic Cordillera include the Prebethic and Subbethic ranges, separated by the Penebethic Depression. The Bethic Cordillera runs along Spain’s southeast coast from Gibraltar to Cabo de la Nao, and extends beyond the mainland to the Balaeric Islands.  It was formed during the Alpine orogeny and Ibero-African collision, and is mainly composed of Mesozoic and Cenozoic basement (Gibbons & Moreno 2003). Rising nearly 3480 m asl and located only 22 miles from the coast, Mulhacén of the Sierra Nevada is the highest peak in the Iberian Peninsula. To the north is the Sierra Morena, which forms the southern end of the Meseta Central and separates the Guadiana and Guadalquivir basins. This area lies on schist, gneiss, and granite bedrock (Sabater et al. 2009).

Freshwater habitats

This ecoregion contains two of the largest rivers in the Iberian Peninsula: the Guadiana and Guadalquivir, which drain the Atlantic Ocean. Both have longer and lower gradients than the Segura to the east due to the gentle slope of the Central Plateau (Sabater et al. 2009).

The Guadiana is fed by many tributaries, some of which originate in the Toledo Range in the northern part of the catchment and karst formations in the Montiel Range (south east). Its basin is flat and wide, with a drop of less than one kilometer from its headwaters to its mouth. Rainfall contributes to most of the Guadiana’s flow via tributaries like the Zújar and Giguela. However, it quickly disappears through the permeable limestone bedrock, resulting in large underground aquifers. Springs are common around impervious layers of the bedrock.  Many of the upper tributaries have intermittent flow, particularly in the summer. Due to high evaporation and low flow, most of these tributaries form underground aquifers, the largest of which is the West Mancha aquifer. The Guadiana flows through mountain lakes (Ruidera lakes), the Tablas de Daimiel wetlands, reservoirs, and numerous small waterfalls. At its mouth the Guadiana forms a small delta and estuary with islands, marshes, and sandbars. Its mean annual discharge is 6.18 km³(Sabater et al. 2009).

The Guadalquivir is the deepest and only navigable river on the Iberian Peninsula. It lies in a depression surrounded by the Sierra Morena to the north and Bethic Cordillera to the south, with headwaters that rise in the Prebethic Range. The river flows southwest to the Atlantic Ocean, fed by high rainfall in the Bethics. Mean annual discharge is 7.22 km³ (Sabater et al. 2009). At its mouth it forms a marsh called the Marismas del Guadalquivir and the Donana marshes, one of Europe’s most important wetlands and protected as a National Park.

The Segura, which flows 325 km into the Mediterranean Sea, is the smallest of the three large rivers. It is separated from the Guadalquivir by the Bethic Cordillera to the north and west, which is also the source of its headwaters. Despite the arid climate in this basin, a few areas of lush vegetation are found in the riparian zone. Most of the river’s flow is regulated by the large number of reservoirs in the basin that divert water for irrigation. An elaborate aquifer system also feeds the Segura. In the lower basin major floods occur in autumn after heavy rainfall, much of which occurs via intermittent tributaries (Sabater et al. 2009).

The ecoregion also includes saline steppe lakes, saline lagoons, coastal marshlands, reservoirs, small lakes, wetlands, and aquifers. One of the most notable areas is Mar Menor, the largest saline lagoon in Spain.

Terrestrial habitats

Four Mediterranean woodland ecoregions comprise Southern Iberia, the largest being the Iberian sclerophyllous and semi-deciduous forests [PA1209], which covers most of the Guadiana and Segura basins and the upper Guadalquivir basin. It is characterized by evergreen broadleaf and conifer canopy species. Other terrestrial ecoregions include the Southwest Iberian Mediterranean sclerophyllous and mixed forests [PA1221] along the lower Guadalquivir basin and Atlantic coast; Iberian conifer forests [PA1208] at higher elevations; and Southeastern Iberian shrubs and woodlands [PA1219] on the Mediterranean coastline. Some of the dominant species in the ecoregion include holm oak (Quercus ilex), cork (Q. suber), Pyrenean oak (Q. pyrenaica), Andalusian gall oak (Q. canariensis), maple (Acer granatense), Aleppo pine (Pinus halepensis), Scots pine (P. sylvestris), and the endemic Spanish fir (Abies pinsapo). Wild olive (Olea europaea and O. maroccana) and carob (Ceratonia siliqua) were once widespread, but now only remnants remain since much of the region has been transformed for agriculture (WWF 2001). Today, agrosylopastoral systems called dehesas are common in this region. It is anthropogenic system that also provides habitat for wildlife. Common tree species include holm oak and cork. Despite the large areas that have been converted the Bethic and Subbethic ranges represent the richest area of endemic plant species in Europe and the Western Mediterranean basin. The Sierra Nevada is particularly noteworthy with the highest concentration of endemic species on the Iberian Peninsula (WWF & IUCN 1994).

Description of endemic fishes

The Iberian Peninsula hosts a large number of endemic species, many of which are limited to Southern Iberia. Of the thirty species in this ecoregion, approximately one-third are strictly endemic. The Guadiana basin alone holds the largest number of endemic fish on the Iberian Peninsula, many of which are highly threatened (Sabater et al. 2009). There are several endemic genera: Iberochondrostoma, Iberocypris, Pseudochondrostoma, and the monotypic Anaecypris. Most of the endemics are cyprinids. The jarabugo (A. hispanica, EN) is a small cyprinid limited to small slow streams in the Guadiana basin. Other endemics include the Oretanium pardilla (Iberochondrostoma oretanum, CR), small-head barbel (Luciobarbus microcephalus, VU), Andalusian barbel (L. sclateri, LC), Guadiana nase (Pseudochondrostoma willkommii, VU), Malaga chub (Squalius malacitanus, EN), bogardilla (Iberocypris palaciosi, CR), and Guadalquivir toothcarp (Aphanius baeticus, EN) (IUCN 2009; Kottelat & Freyhof 2007). The Andalusian barbel is endemic to the central and southern Iberian Peninsula, including the Guadiana, Guadalquivir, and Segura basins (Sabater et al. 2009).

Other noteworthy fishes

Southern Iberia contains a number of threatened fish, including the critically endangered Oretanium pardilla (Iberochondrostoma oretanum) and Atlantic sturgeon (Acipenser sturio). The last known Atlantic sturgeon was caught close to the Guadalquivir estuary in 1992. Other interesting species are the calandino (Iberocypris alburnoides) and cacho (Squalius pyrenaicus), which interbreed (Kottelat & Freyhof 2007).

Ecological phenomena

Migratory species in the ecoregion include the catadromous European eel (Anguilla anguilla); and anadromous Allis shad (Alosa alosa), Twaite shad (A. fallax), Atlantic sea lamprey (Petromyzon marinus), and Atlantic sturgeon (Acipenser sturio), last caught near the Guadalquivir estuary in 1992 (Kottelat & Freyhof 2007).

Justification for delineation

Southern European ecoregions were delineated based on a bottom-up approach employing both published and unpublished field data and expert assessment (Abell et al. 2008; Doadrio 2001). Southern Iberia is related to the Riff Mountains in Morocco and was placed between the European and North African plates (Meulenkamp & Sissingh 2003). For this reason some common elements are preserved on either side of the Strait of Gibraltar (e.g. Luciobarbus, see Machordom & Doadrio 2001; or Cobitis, see Doadrio & Perdices 2005). The posterior evolution of Southern Iberia with the lifting of the Bethic Mountains resulted in a well differentiated freshwater fish fauna.

Level of taxonomic exploration

Fair, although new species might be described.