Taisha is the author of today’s entry:
This rare species is endemic to the Canary Islands, where it is known from the northeast coast of Tenerife, near El Sauzal in the Anaga region. It grows at the base of basalt cliffs with conglomerate outcrops between 20 to 30 or more meters above sea level. Lotus maculatus is listed as “critically endangered” on the IUCN Red List of Threatened Species as: 1) it is restricted to a single location of only one square kilometer; 2) there are fewer than 50 individuals this species; and 3) there are ongoing threats to this species due to grazing, hiking, collection, and other human-related activities.
Parrot’s beak or lotus vine is a woody-based subshrub that can have stems reaching 2.5 meters in length when growing among rocks. More commonly, plants have stems of ca. 30cm in cultivation. The linear leaves with 5 leaflets are odd-pinnate, or imparipinnate–meaning they are pinnately-compound leaves with a single terminal leaflet. The zygomorphic and terminal flowers are yellow but turn to orange at the tips, with an obvious black stripe upon the standard petal or banner. The fruits of this species are legumes that have 2 valves, with many dark spherical seeds within. (see: Hind, N. 2008. Lotus maculatus. Curtis’s Botanical Magazine. 25(2):146-157 doi:10.1111/j.1467-8748.2008.00613.x).
In the above-mentioned article, it is noted that members of the subgenus Rhyncholotus (of which this species belongs) possess a number of floral traits suggesting they are specialist-pollinated by birds (i.e., they are ornithophilous). The traits listed include red-orange-yellow corollas, scentless flowers, and high nectar production. However, there are some curiousities associated with this: in Macaronesia (including the Canary Islands), there are no specialist nectar-feeding birds and these presumptive ornithophilous-flowered taxa are present on the islands but absent in nearby northwest Africa and Europe.
Several hypotheses were made to explain the evolution of ornithophily in the group. The “de novo specialist” hypothesis proposed that now-extinct nectarivorous bird species placed selective pressures on members of this genus (with these species only now being maintained by opportunistic birds). The “relict hypothesis” proposed that the bird-pollinated syndrome evolved on mainland Africa before the colonization of the Macronesian islands. After colonization of the islands, opportunistic birds replaced the specialist birds. Lastly, the “de novo opportunistic hypothesis” proposed that the floral features evolved on the islands due to the selective pressures by opportunistic birds. It is noteworthy to mention that there has been no fossil evidence of specialist pollinator birds found on the Canary Islands. While the origin of ornithophily is still unknown, a recent analysis supports the de novo opportunistic hypothesis (see: Ojeda, I., Santos-Guerra, A. 2011. The intersection of conservation and horticulture: bird-pollinated Lotus species from the Canary Islands (Leguminosae). Biodiversity Conservation. 20: 3501-3516.).