Puya raimondii is rivalled only by members of the Ceroxylon
palm genus as the most spectacular high-Andean plant. It occurs in often
very isolated and usually small populations or rodales from Peru
to Bolivia. Communities
frequently number a few hundred individuals or less, but can range up to perhaps 30,000 plants in Paso Winchus as well as in Cashapampa, Pachacoto and
sector Carpa, Huascarán National Park, Huaraz, which is probably Peru’s best
known location. Populations reach 10,000 in Rodeo, Arani
largest population which may represent one third that country’s plants. In Titankayoc in southern Peru’s Ayacucho,
however, there is an extraordinary site of several thousand hectares which
contains, depending on source, an estimated 250,000 to at least 450,000 plants.
With this arguable anomaly, the plant’s sporadic and scattered distribution and
extreme genetic homogeneity, detailed below, suggest the vestigial remains of a
species in decline. Outside its habitat,
there appear to be no more than two dozen mainly small specimens in perhaps
half a dozen botanical gardens.
The plant is monocarpic and in
habitat seeds only once in about 80 years or more before dying. Although
a mature Puya will produce 8–12 million seeds
and viability is usually good, inclement montane conditions at the time of
dispersal, which may inter alia affect
pollinating insects, can result in few if any germinations. Moreover, seeds in less than ideal conditions can begin to lose germinating
ability after a few months and are also susceptible to damping-off.
Because of these factors, a century-old plant may not reproduce at all and
will, botanically, have lived in vain. This risk is exacerbated
by global warming whose effects on Peru’s glaciers are well established. Climate change may already be impairing Puya raimondii’s ability to flower (Venero pers. comm.).
In the wild, these plants seem to be exceedingly choosy about where they grow. Their seeds
are very small and by design easily wind-blown. Yet even in undisturbed
locations P. raimondii can limit itself
to one small spot although edafic, topographic and microclimatic conditions in
the surrounding area appear identical.
The species is officially considered
endangered in Peru
(Law No 043- 2006-AG). But in practical terms this means little, if
anything and only the country’s best-known rodales (Puya communities) benefit from some protection. Elsewhere, the plant can
be the object of hostility and large stones are often thrown at them, lodging
for years among the leaves. Cattle roam
unfettered among many colonies which are not being regenerated because the
animals either trample or may eat juveniles. In other sites, fires are
set to create pastureland or the thorny leaves are burnt to facilitate access
to the trunks' starch which becomes cattle fodder. Pith removal, of course, kills the plant.
Compounding all these issues,
there is exceedingly little genetic variety within existing populations. A
genomic DNA analysis (Sgorbati et al.) of the genetic structure of eight
populations (including the huge one at Titankayoc) representative of P. raimondii in Peru detected just 14 genotypes in
160 plants. Only a few of the 217 AFLP
marker loci screened were polymorphic and four populations were completely
monomorphic. Less than 4% of the total
genomic variation was within populations and genetic similarity among
populations was as high as 98.3%. Flow
cytometry of seed nuclear DNA content and RAPD marker segregation analysis of
progeny plantlets demonstrated that the extremely uniform genome of these
populations is not compatible with agamospermy but the result of inbreeding. Many rodales have
disappeared only recently, as proved by vernacular Puya names still in local use. Even though fully fitted to its
harsh environment, P. raimondii lacks
sufficient variability in its genome and, possibly also phenotype variability
to allow it to adapt to both anthropic pressure and present climate change.