Pinus radiata var. binata (Engelm.) Lemmon

Pinaceae

Endemic to two small islands off the coast of Baja California, Mexico: the main threats are pitch canker, impacts of possibly frequent fires, climate change, and introduced species

Associated Names:

Distribution

Mexico. Recorded from Guadelupe Island, an uninhabited island 250km off the mainland, and from Cedros Island (part of Baja-California). The name P. binnata var. cedrosensis is used by some people, for the Cedros Island population.

The pines on Guadalupe Island are narrowly distributed at the north end of the island, along the uppermost slopes of the central ridge.

On Guadalupe Island, the subpopulation has 200–250 (over-) mature trees and several hundred seedlings. On Cedros Island, there are two main subpopulations: a central and northern subpopulation, separated by approximately 13km, with some scattered trees and small stands outside these two occurrences. The pines are largely restricted to the upper, western slopes of the northern mountain range, which extends from the central to northern regions of Cedros Island in roughly a north-south alignment. There is no comprehensive census, but there are thousands of trees and no apparent losses of habitat over the last several decades. In May 2001, the pines were described as fairly young over much of the current range, with seedlings in all stands

Habitat and Ecology

This variety forms small stands or grows as isolated trees on Guadalupe Island; on Cedros Island it is more often associated with other trees.

Human Uses

No uses are recorded of this variety. It is known that seeds were collected and used to raise plants, but unknown if these have found their way outside nurseries that grew them as an ex-situ conservation effort. As far as known, all widely planted trees of Monterey pine are of provenances from the mainland variety radiata.

Conservation Status

Global status

Vulnerable D2

Global rationale

The successful eradication of goats recently on Guadalupe Island raises expectations that the subpopulation on that island may recover from a low of ca. 250 (over-)mature trees at present. The subpopulation(s) on Cedros Island are larger (a few thousand trees, but no census made) and regenerating well in the absence of goats.The restricted area of occupancy and two locations on two islands and the existence of a deadly pathogen affecting the mainland variety of this species puts the island variety at risk if that pathogen was introduced on one or both of the islands. It meets criterion D2 for the category Vulnerable

Global threats

This variety, confined to two islands, was until very recently under serious threat from feral goats on Guadalupe Island, which is almost uninhabited. It is estimated that only 200–250 (over-)mature trees remain there and reproduction is scarce. On Cedros Island, although the pines are currently regenerating well, they remain vulnerable to the introduction of pitch canker from the nearby Mexican mainland, and to the uncertain impacts of possibly frequent fires, climate change, and some introduced species. No evidence of the pitch canker disease (caused by the fungus Fusarium circinatum) that has affected mainland (California) subpopulations of P. radiata var. radiata was found on either island.

Conservation Actions

Total eradication of goats appears to be difficult, but apparently has been achieved recently. Exclosures to keep goats out of some of the most sensitive areas have been realized with help from outside and this has helped establishment of several hundred pine seedlings. Pinus radiata var. binata does better on Cedros Island which has (had) no feral goats. It is hoped that with the removal of goats on Guadalupe Island the population will increase in future.