Punta Ballena is the coastal southern tip of the Sierra de la Ballena, a shear zone of two tectonic plates, located at the beginning of the oceanic coast of Uruguay. Coastal rocky points are especially relevant because of their high plant richness, moreover their vegetation is endangered mainly due to the high tourist – urbanistic development of the coast. This study aimed to determine the list of vascular plants occurring on Punta Ballena coastal rocky point and identify its vegetation communities. Also, to identify endemic species, threatened and of interest for conservation species; and to analyze the species historically documented for the site. Punta Ballena stands out for its remarkable species richness with 427 species, dominated by Asteraceae (82), Poaceae (82) and Fabaceae (26). Five vegetation types were found in the natural area, which allows the combination of species with different adaptations. The site supports five vulnerable species and one endangered species (IUCN), 33 priority species for conservation, two local endemisms and numerous national (13) and regional (45) endemisms. Regarding historical collections, to date Punta Ballena has suffered a loss of 14% of its species, this is likely a direct consequence of the recent urban development. From these historically documented species, we consider five of them to be locally extinct. Due to these overwhelming results, we consider the site a diversity hotspot on the Uruguayan coast. It becomes urgent to generate conservation plans that allow the maintenance of the flora and vegetation communities that are still preserved in the area.

coastal rocky point, endangered site, endemisms, historical collections, local extinctions, species list, threatened species, vegetation types

The Uruguayan coastline has an extension of 473 km on the la Plata River and 233 km on the Atlantic Ocean (Goso et al. 2011), along which a great diversity of environments such as rocky points, beaches, dune fields, lagoons, psammophilous shrublands and forests have developed (Alonso Paz and Bassagoda 2003). This diversity of environments supports a great floristic richness, with estimations of about a third of the country’s flora species present in a 10 km-wide coastal strip (Alonso Paz and Bassagoda 2006). Among these environments, rocky coastal points are of special relevance because of their high plant richness and particular species composition.

Geologically, the estuarine and oceanic coast of Uruguay shows a great diversity of rocky materials and sediments; where coastal rocky points show a varied geological evolution (Goso and Muzio 2006). Vegetation associated with coastal rocky points is adapted to the environmental stress conditions given by the oceanic influence, such as strong winds, wave action, high salinity levels and permanent insolation (Chebataroff 1942, 1950; Alonso Paz and Bassagoda 2006). Among the numerous rocky coastal points on the coast of Uruguay, only two of them have previous studies that describe their flora and vegetation: Cabo Polonio (Delfino and Masciadri 2005; Masciadri et al. 2006; Picasso and González 2015) and Cerro Verde (Alonso Paz and Bassagoda 2003), and both are protected areas included in the National System of Protected Areas (IMPO 2021). Punta Ballena has been highlighted as a site with high plant diversity in technical reports (Bonifacino s.d., Rodríguez-Gallego et al. 2008) and was proposed as a relevant remnant patch of coastal vegetation (Puppo et al. 2020).

Vegetation occurring on coastal rocky points is exposed to alterations and threats due to the high tourist – urbanistic development that the coastal strip has been experiencing for decades (Alonso Paz 2005; Delfino and Masciadri 2005; Marchesi et al. 2013). Additionally, in these environments, the extraction of plants mainly due to collectors or for ornamental purposes affects their populations (Marchesi et al. 2013). Moreover, Fagúndez and Lezama (2005) considered the vegetation associated with coastal rocky points to be in need of conservation, due to their low occurrence and their presence on reduced surfaces, and suggested that their persistence is seriously threatened unless urgent measures are taken for their protection.

In view of the scarce previous research and the rapid degradation of this unique ecosystem, the aim of this study was to generate a list of vascular plants found on the coastal rocky point of Punta Ballena and to identify their plant communities. In order to contribute to the development of conservation plans, this work sought to identify species that are endemic, threatened and of interest for conservation, as well as analyze the species historically documented at the site, and evaluate which ones are still present and which ones are extinct. The complete plant species list with life form assessment, type of record and reference voucher, vegetation type where each species occurs, geographic origin, conservation status and endemism information is detailed.

A total of 427 species were registered on the Punta Ballena rocky point, distributed in 252 genera and 71 families (Table 2). Asteraceae and Poaceae were the richest families (82 spp.); the subsequent families with large contributions were Fabaceae (26 spp.), Cactaceae (14 spp.), Cyperaceae (14 spp.), Iridaceae and Solanaceae (12 spp., each one), Amaryllidaceae and Rubiaceae (11 spp., each one); the remaining families have fewer than 10 species, most of them having fewer than three species (Table 2).

Figure 2. 

Aerial view and vegetation types of Punta Ballena. A: Aerial view of the natural area of Punta Ballena rocky point; B-C: rupicolous herblands and detail of the rocky substrate; D: mesophilic herblands associated with implanted Racosperma longifolium patches (in the background of the photo); E: hydrophilic herblands; F: halophilic grasslands; G: humid rocky shelters communities; H: native forest patches; I: Vegetation of disturbed areas on the access road (A-M. Bonifacino photo).

Life forms and vegetation types

Herbs were dominant in the studied flora (76%), with a major representation of ‘evergreen herbs’, ‘grasses and graminoids’ and ‘therophytes’ (21, 20 and 19%), followed by ‘seasonal herbs’ (which persist through subterraneous or basal resistant structures) which reached almost 16%. They were followed by suffrutex (9.6%), shrubs (4.2%) and cactus (3.5%). Less representation was shown by ‘ferns and lycophytes’, ‘veins’, ‘trees’ and ‘arborescent monocots’ (less than 2% each) (Fig. 3).

Figure 3. 

Species number of plant life forms found in Punta Ballena.

Five main native vegetation types were found in the natural area of Punta Ballena rocky point (Figs 1C, . 2): ‘halophilic grasslands’, ‘humid rocky shelters communities’, ‘hydrophilic herblands’, ‘mesophilic herblands’ and ‘rupicolous herblands’. The latter vegetation type on the eastern slope is associated with implanted "Racosperma longifolium patches" (Table 2, Fig. 1C). Two additional vegetation types were found on the sides of the access road: ‘native forest patches’ and ‘vegetation of disturbed areas’. ‘Rupicolous herblands’ developed over and between rocks, or in places near rocky outcrops with scarce soil availability (depth less than 10 cm); this is the most extensive vegetation type in the area covering nine ha. ‘Mesophilic herblands’ developed in areas higher than 20 m above sea level on long slopes of the rocky point, where soil is close to 50 cm deep; it occupied 5.3 ha, of which 0.4 ha corresponded to ‘Racosperma longifolium patches’. ‘Halophilic grasslands’ occur in sites exposed to temporary floods from de la Plata River on the extreme point, with scarce substrate mainly composed of sand, pieces of rock, and decomposing materials; this vegetation covered less than 0.3 ha. ‘Hydrophilic herblands’ developed in depressions between rocky areas or low areas of the slope, and were found only on the west slope of the rocky point. It had the deepest substrate, more than 80 cm deep, and occupied approximately 0.15 ha. ‘Humid rocky shelters communities’ developed on the rocks exposed to the tide and reached negligible surface coverage (< 0.1 ha).

‘Rupicolous’ and ‘mesophilic herblands’ were the vegetation types with the highest number of species, maintaining 35% and 34% of the flora, respectively. A high number of species could develop in both vegetation types (48 species, 13%) as well. These were followed by ‘hydrophilic herblands’ (25 species, ca 7%) and ‘halophilic grasslands’ (13 species, ca 3%), ‘humid rocky shelters communities’ showed less significance with 4 species (<1%). ‘Native forest patches’ and ‘vegetation of disturbed areas’ on the sides of the access road reached 12 and 13 species respectively (ca 3% each).

Endemisms and threatened species

Punta Ballena supported a high number of threatened and priority species for conservation, as well as endemisms, summing up 74 taxa, 17% of the site flora (Table 2, Fig. 4). According to IUCN criteria, Cypella osteniana, is considered endangered (Paz Deble et al. 2021) and five species are vulnerable: Oxypetalum marchesii (González et al. 2018) along with four Cacti: Parodia concinna, P. ottonis, P. scopa and Parodia sellowii (it should be noted that Parodia tabularis, was not evaluated by IUCN). A total of 33 taxa were considered priority for conservation in the country and 64 were identified as endemic: 48 regional endemisms, 13 with a restricted distribution within Uruguay and two local endemisms from Punta Ballena: Senecio ostenii var. balaenicus and Parodia tabularis (Table 2, Fig. 4).

Figure 4. 

Priority for conservation and threatened species from Punta Ballena. Amaryllidaceae: A: Beauverdia hirtella, B: Zephyranthes estensis. Apiaceae: C: Apium prostratum. Arecaceae: D: Butia odorata. Asclepiadaceae: E: Oxypetalum marchesii. Asteraceae: F: Aldama nudicaulis, G: Grazielia brevipetiolata, H: Porophyllum brevifolium, I: Schlechtendalia luzulaefolia, J: Senecio ostenii var. balaenicus, K: Sommerfeltia spinulosa, L: Trichocline incana. Cactaceae: M: Cereus uruguayanus historic photo, taken from the herbarium specimen Osten 16506 (MVM), N: Frailea pygmaea, O: Gymnocalycium hyptiacanthum, P: Opuntia arechavaletae, Q: Parodia concinna, R: Parodia ottonis, S: Parodia scopa, T: Parodia sellowii, U: Parodia tabularis, V: flower detail of Parodia tabularis. Caryophyllaceae: W: Spergularia rupestris. Crassulaceae: X: Crassula caudiculata. Cyperaceae: Y: Carex vixdentata, Z: Eleocharis montevidensis. Euphorbiaceae: Aa: Croton nitrariifolius. Fabaceae: Ab: Mimosa amphigena var. trachycarpoides, Ac: Mimosa reptans. Iridaceae: Ad: Cypella osteniana, Ae: Sisyrinchium rosengurtii. Malvaceae: Af: Pavonia cymbalaria. Orchidaceae: Ag: Bipinnula gibertii, Ah: Bipinnula montana. Poaceae: Ai: Echinochloa polystachya var. spectabilis. (H, S, Y and Ac-S. Fernández Photos).

Despite the fact that several historically documented taxa were currently confirmed in the site, 14% of the total taxa had not been registered in recent years. Applying a precautionary principle, these taxa were kept on the species list. Due to the lack of exact data from the collection sites of some historic specimens, as well as the urban development of the site (which has led to the loss of native environments and their vegetation), these taxa could either be present with diminished populations or be locally extinct. In this sense, we confirm five species as locally extinct: Oxypetalum nigricans, Gyptis commersonii, Gyptis tanacetifolia, Agalinis digitalis and Parodia mammulosa (Table 2, Fig. 5).

Figure 5. 

Species with historic record for Punta Ballena, considered regional and Uruguayan endemisms or priority for conservation for the country. Black box indicates species locally extinct. Asclepiadaceae: A: Oxypetalum nigricans. Asteraceae: B: Baccharis arenaria; C: Baccharis gnaphalioides; D: Gyptis commersonii; E: Gyptis tanacetifolia; F: Panphalea heterophylla. Cactaceae: G: Parodia mammulosa. Cyperaceae: H: Cyperus berroi. Euphorbiaceae: I: Croton chamaepitys. Hypericaceae: J: Hypericum piriai. Orobanchaceae: K: Agalinis digitalis. Poaceae: L: Jarava juncoides; M: Aristida filifolia; N: Aristida murina; O: Aristida teretifolia; P: Danthonia rhizomata; Q: Digitaria enodis; R: Piptochaetium confusum.

Punta Ballena stands out because of its high plant diversity (427 spp), especially considering that only 20 ha. are currently in a natural state. This species list corresponds to 15% of the total flora of the country (2756 spp, Marchesi et al. 2013). The particular geological characteristics of the site, where geological materials of different origins converge (Goso and Muzio 2006; Spoturno et al. 2012), and the continuity of the hill environment towards the sea, have surely allowed the development of this varied flora.

The most species-rich families, Asteraceae and Poaceae, followed by Fabaceae, coincide in being the families with the highest species richness for the country and dominate the “Rio de la Plata grasslands” ecoregion, where Uruguay is located (Andrade et al. 2018). Also, other numerous families of Punta Ballena, are characteristic of this ecoregion, such as Cyperaceae, Solanaceae and Rubiaceae. The importance of Cactaceae and Cyperaceae in this site is highlighted, first because they are species that grow between and over rocks, and second because its species grow in humid environments, with permanent or temporary accumulation of water, which occurs in some sectors of the rocky point.

The projection of the rocky environment into the la Plata River, and the presence of several microhabitats allow the development of different vegetation types at the site (Figs 1C, 2). This vegetation diversity found on the rocky point sustains species with different habitat affinities, such as rupestrian and epilithic species in rupicolous herblands, halophyte species either in rupicolous herblands influenced by the sea or in halophilic grasslands, and a combination of grass and herbs in mesophilic herblands (dominated by Asteraceae, Fabaceae and Poaceae spp.). As expected for the preponderant vegetation, herbs were dominant in this flora with a major representation of perennials. They have developed several strategies to grow in this environment; in this sense rosettes and prostrate or decumbent habits were widely recorded, as well as specialized subterranean structures such as xylopodia, bulbs, rhizomes or thickened stems and roots. Species that develop in halophytic grasslands exhibit adaptations to live in saline environments, such as succulent leaves, salt excretory glands, and the ability to maintain a relatively high osmotic pressure in their tissues due to salt accumulation (Chebataroff 1936, 1950; Legrand 1959). Shrubs and suffrutex are also common, being habits developed by species that in other environments acquire greater size but here, grow in a squat and prostrate way. A frequent adaptation to the rocky environment is succulence; in this site Cacti stands out for developing succulent, globose or cladode stems.

Regarding historical collections from the site, to date Punta Ballena has suffered a loss of 14% of its species. This fact is likely a direct consequence of the urban development of the site in recent decades. Even, from the historically documented species, we consider five species to be locally extinct: Oxypetalum nigricans, Gyptis commersonii, Gyptis tanacetifolia, Agalinis digitalis and Parodia mammulosa (Fig. 5). For all these taxa there was a reduction of their typical environments and in those that remain they were not found. In turn, during the continuous surveys we could confirm that some species showed severely diminished populations such as: Frailea pygmaea, Gymnocalycium hyptiacanthum and Lathyrus subulatus, with scarce individuals or populations in the area. Specifically, in relation to Cacti, in addition to verifying the absence of Parodia mammulosa, we note a decrease in the abundance of all Cactaceae species, probably as a consequence of illegal collection.

The site supports five vulnerable and one endangered species (IUCN), numerous priority species for conservation in Uruguay, two local endemisms and numerous national and regional endemisms (Table 2). Most of the priority species are widely distributed along the rocky point: e.g. Apium prostratum; Aldama nudicaulis, Grazielia brevipetiolata, Porophyllum brevifolium, Schlechtendalia luzulaefolia, Sommerfeltia spinulosa, Trichocline incana; Spergularia rupestris; Croton nitrariifolius; Sisyrinchium rosengurtii; Pavonia cymbalaria; Jarava juncoides and Nassella pauciciliata. Moreover, among the endemic taxa, the regional endemisms denote the mixture of campestre species with subtropical species that show atlantic or paranaense affinity: e.g. Beauverdia sellowiana, B. vittata; Aldama nudicaulis, Baccharis patens; Frailea pygmaea, Parodia concinna, P. mammulosa, P. scopa; Mimosa ramulosa, M. reptans; Herbertia pulchella; Bipinnula gibertii and B. montana. The taxa with a restricted distribution within Uruguay could be found throughout the rocky point, e.g. Beauverdia hirtella and Zephyranthes estensis; Oxypetalum marchesii; Grazielia brevipetiolata, Porophyllum brevifolium; Spergularia rupestris; Mimosa amphigena var. trachycarpoides; Cypella osteniana; Nassella pauciciliata; among others. Finally, two local endemisms from Punta Ballena are present at the site: Senecio ostenii var. balaenicus and Parodia tabularis (as was previously mentioned, the latter has shown a reduction in its population each year).

Most of the species were native, while exotic species represented 13% of this flora. Many of them (11 species) were considered IAS for the country (Masciadri et al. 2010). Carpobrotus edulis is of greater concern in the site, because it is locally spreading in the rupicolous communities of the rocky point. Another IAS at the site is Cynodon dactylon, which develops a dense tapestry in some sectors of the mesophilic herbland, especially near parking lots or in places prone to be altered or disturbed. Pittosporum undulatum is mostly found on the sides of the access road, while Ulex europaeus was locally restricted to a sector of the rocky point. The remaining IAS coexist with native species integrating the different types of vegetation. All these species represent a threat for the vegetation, the diverse flora of Punta Ballena and the numerous species of interest for conservation. Masciadri et al. (2010) suggested that rapid actions be carried out to control IAS specially in coastal departments of Uruguay, not only to reduce the negative impacts on coastal ecosystems, but also to mitigate the economic losses related to IAS that could happen in a locality that relies on tourism.

The highly diverse flora of Punta Ballena, as well as the documented presence of numerous taxa with interest for conservation and endemisms on a reduced surface, justify the urgent need for protection of the site. It is especially necessary to regulate common actions that occur on the natural area of the rocky point, such as cutting grass and herbs on the sides of the access road (that reduce natural populations of some native species, in contrast to adventitious and exotic ones); vehicular traffic or irregular parking in areas with vegetation or rocks (that not only affects plants but also the fauna associated with it); restrict the parking surface (that has increased in recent years); and finally take actions to avoid the illegal extraction of specimens of cactus and other species by visitors. In relation to the urbanized area, the projection of an urban advance in natural remnants, would lead to the extinction of numerous species, many of which have previously been classified as priority for conservation or under IUCN threat categories. Additionally, it is necessary to regulate the types of plants used in gardens and for green roofs, since several species commonly used are exotic and IAS, and represent a threat to the native vegetation of the site.

Some recommendations to promote the conservation of the area: in the private area, all non-developed private spaces should not be intervened with, the natural vegetation of the place should be promoted and maintained, and land leveling or other modifications of the natural terrain should not be allowed. In the public natural area, it is necessary to take actions to regulate traffic and irregular parking in areas where there is vegetation, and avoid or minimize the cutting of grass. Additionally, boardwalks with explanatory and informative signs should be incorporated, and a species protection site should be promoted in this particular area, given that it is a hotspot on the coast of Uruguay.

Our work highlights the floristic importance of the emblematic coastal site of Punta Ballena. We consider the natural area of this rocky point as a plant hotspot, because it supports an exceptionally high flora and nourishes a significant number of endemic, priority for conservation and threatened species. The loss or decrease in surface area of this natural space would seriously endanger the existence of all these species. From a conservation perspective, we hope this work lays the foundation to generate conservation plans for the site and for the future definition of actions and responsibilities.

The authors thank the curators of the herbaria, and specially MVJB where the specimens of this research were deposited. Special thanks are due to N. Idjiloff, S. Fernández, L. Rodríguez-Tricot and M. Zarucki for their participation in fieldwork; F. Lezama and F. Haretche for confirmation and determination of some specimens, and M. Bonifacino and S. Fernández for the contribution of photos. This research was funded by CSIC-UdelaR. P.M. thanks PEDECIBA and ANII for the granting of a PHD thesis scholarship.