Pitcairnioideae rival Tillandsioideae for oral variety and kinds of pollinators attracted. Also, tendencies to deviate from basic designs characterize some clades more than others. Reproductive structure and pigmentation suggest near to complete dependence on insects for Brocchinia, Cottendor a, Deuterocohnia, Dyckia, Encholirium, Fosterella, Lindmania and Hechtia. Conversely, in orescence shape (massive cylindrical to loose paniculate), diverse ower colors, radial to zygomorphic corollas, hypoge-nous to epigenous architecture and observations in situ indicate that more varied fauna service Pitcairnia and Puya. Pronouncements about Navia

(probably many syndromes, but no entries in Table 6.1) and some of the other Guayanan endemics would be premature. At this point, Pitcairnia more than any of the other pitcairnioid genera compares with Guzmania, Tillandsia and Vriesea for oral variety.

Members of Pitcairnia (sensu lato), which is the largest genus (>250 species) within its subfamily, mostly produce elongate tubular owers with actinomorphic to moderately zygomorphic corollas, which in the second case open on one side below the intertwisted petal tips to expose anthers and stigma (Fig. 3.4F,H,K,L,M). Further embellishments heighten appeal to birds (red corolla, copious nectar, diurnal presentation; e.g., P. corallina, P. nubigena), bees (white, yellow to green petals, lesser amounts of nectar, diurnal opening; e.g., P. brevicalycina, P. albi'os), moths (white corolla, strong odor, abundant nectar, crepuscular/nocturnal anthesis; e.g., P. 'ammea var. pallida, P. unilateralis) and bats (pale corolla, unpleasant night odor, abundant, exposed nectar; e.g., P. loki-schmidtiae, P. palmoides).

Pitcairnia mbriato-bracteata surely ranks among the most exceptional species relative to oral biology. Reddish owers born on an equally garish, sinuous in orescence extend from what by anthesis has become a glutinous mantle of autodigested, brownish, overlapping oral bracts. More modest deliquescence characterizes additional species such as P. arcuata (Fig. 3.4M). Pitcairnia rubro-nigri'ora holds the record for striking ower color with an almost black-purple corolla contrasting with the bright red calyx. A comparably red in orescence produced by Pitcairnia corollina snakes along the ground, exposing foraging birds to terrestrial predators, unless of course typically precipitous substrates, often cliff sides, reduce this threat.

Bat-serviced Pitcairnioideae, like comparable Tillandsioideae, manipulate pollinators with scents, abundant nectar, and owers and in orescences organized along two patterns. Chiropterphilous Pitcairnia and Puya display large, well-separated and exposed owers that open sequentially to present extended, tubular perianths enclosing often clustered stamens (Fig. 3.4H). Pale to greenish petals that form a more or less wide-mouthed gullet and musty, nocturnal fragrances further distinguish these taxa from orni-thophilous relatives. Conversely, Encholirium glaziovii, the bromeliad with the most thoroughly documented dependence on bats (Sazima et al. 1989), like much of the rest of its genus, produces a cylindrical brush-type, many-owered (>200) spike 1.5 1.8 m tall (Figs. 3.4G, 6.2A). For about 10 days, relatively small, protogynous owers, each with a wide mouth, persistent (several days) perigon and stiff, spreading stamens and style, bloom in a wide acropetal belt (Fig. 3.4G). Enough dilute nectar (4.6% solids) issues

Figure 6.2. Habits and seeds of certain Bromeliaceae. (A) Unidenti ed Encholirium in Bahia State, Brazil. (B) Hechtia schottii in Yucatán State, Mexico. (C) Fruiting monocarpic Tillandsia utriculata in south Florida. (D) Seeds of Tillandsiapaucifo-lia glued in groups of four to the bark of Taxodium distichum in south Florida in the manner employed to test germination.

Figure 6.2. Habits and seeds of certain Bromeliaceae. (A) Unidenti ed Encholirium in Bahia State, Brazil. (B) Hechtia schottii in Yucatán State, Mexico. (C) Fruiting monocarpic Tillandsia utriculata in south Florida. (D) Seeds of Tillandsiapaucifo-lia glued in groups of four to the bark of Taxodium distichum in south Florida in the manner employed to test germination.

from the many simultaneously active gynoecia to ow down the grooved in orescence axis.

While chiropterophilous Tillandsioideae typically inhabit dense, humid montane forests as epiphytes and attract diverse phyllostomids, terrestrial Encholirium glaziovii more closely parallels similarly pollinated Mexican Agavaceae. Populations occupy open, semiarid, rocky scrub communities characteristic of the "campos rupestres of interior southeastern Brazil (Fig. 1.4C). Its single bat visitor at the study site, trap-lining Lonchophylla bokermanni, hovered to collect nectar beginning about 30 60 min after dusk. Visits at 5 40-min intervals consisted of several wide loops around a spike interrupted by nectar collections that lasted less than a second, yet long enough to brush pollen on and off the animal s snout. Several other ower-dependent bats in the same area ignored E. glaziovii, apparently preferring less exposed food plants in nearby gallery forest and cerrado. Sphingids and some other moths sporadically visited the same E. glaziovii owers.

Exclusively Guayanan Navia (~ 100 species) contains many narrowly distributed lithophytes. The small owers born by many taxa are probably inadequate to satisfy the caloric needs of vertebrates. During anthesis brightly pigmented foliage highlights sessile, somewhat larger owers born in the typically capitate sessile in orescences of one group of relatively robust species. Just the proximal portions of the younger leaves color up to deep orange/red (e.g., N. arida), or they bleach to brilliant white (e.g., N. jauaensis). Foliar pigmentation changes little in other instances, that role falling to the oral bracts (e.g., N. splendens). Densely congested owers with somewhat oversized stigmas and anthers presented above the shoot suggest anemophily or dependence on small insects in another part of the genus (Fig. 3.4A C).

Even fewer records address Connellia ( ve species) from the same poorly collected, remote upland habitats. Corollas are showy, rose-pink in C. smithiana, and location among the leaf-like bracts suggests pollination by Hymenoptera. Most of the remaining larger genera (Cottendor a, Dyckia, Hechtia, Fosterella), and several lesser ones (e.g., Brewcaria, Steyerbromelia), exhibit principally entomophilous, relatively small, open owers in a variety of mostly pale pastels. Fosterella spectabilis alone in its otherwise white to cream- owered genus probably attracts birds with a coral red, predictably more elongated corolla (Luther 1997; Fig. 3.4D).

Members of Puya, the second largest of the nearly 20 pitcairnioid genera, also utilize diverse pollinators through mostly Andean ranges. Ortiz-Crespo (1973) observed specimens in the botanical gardens at the

University of California at Berkeley and in situ in Ecuador. Plants at both locations produced concentrated nectar from relatively large, often bluish to green, showy owers rendered additionally conspicuous by bright orange anthers. Tubular corollas, unaccompanied by scent, the production of sticky pollen and a simple stigma further implicated birds as the primary vectors. Colibri coruscans, and a few, much larger Patagona gigas, maintained near continuous presence, while a colony of Puya aequatorialis owered for about six weeks at a site approximately 20 km north of Quito, Ecuador. Small, agile Colibri coruscans, the most aggressive of the lot, often denied two or three additional hummingbirds access to nectar. In orescences had been under its surveillance for several days before the rst owers opened.

Other Puya species reportedly serviced by hummingbirds include P. chi-lensis (yellow owers), P. berteroniana and P. venusta (most consistently by Patagona gigas). Flocks of hungry Austral blackbirds (Curaeus curaeus) also visited P. chilensis. In orescence and ower structure either encouraged or denied use by additional nches and ycatchers according to ight and feeding behaviors (Johow 1910). Species that lack sterile extensions on the lateral axes of what are usually dense panicles also possess owers with deep corolla tubes (subgenus Puyopsis; e.g., P. venusta) to discourage all but the hover iers. Those taxa (subgenus Puya; e.g., P. chilensis) able to accommodate perching birds also offer shorter owers accessible to ying and stationary feeders alike. The diurnal moth Castnia eudesmia feeds both as a larva and as an adult on some of the same Chilean Puya species. Its reputed ability to drive similarly disposed insects and even birds from favored food sources warrants further study.

Abundant nectar disposes the larger-bodied Puya species for ornitho-phily; requirements to set fruit, especially the monocarps, and often hyper-dispersed populations may permit no alternatives. Few other trap-liners range into paramo and puna formations where Puya often dominate otherwise sparse oras (Fig. 14.2C). Certain high-elevation species strengthen the case for obligate dependence on powerful iers to the extent that their self-incompatibility characterizes the other alpine Puya. Puya mirabilis (self-compatible) and P. ferruginea demonstrate the feasibility of chiropte-rophily at lower elevations. Insufficient capacity to support ower visitors with high caloric demands may help explain the absence of many additional Pitcairnioideae and more than a modest contingent of Tillandsioideae at these same cold, barren sites. The importance of plant size to frost-tolerance in tropical alpine habitats may further limit the success of Bromeliaceae above the tree line (Chapters 4 and 7).

Varadarajan and Brown (1988) considered stigma morphology diagnostic for the primary pollinators of certain Pitcairnioideae. For example, orni-thophilous Pitcairnia usually possess compact, conduplicately folded stigmas (Figs. 3.1C, 12.1) bearing spathulate lobes covered with densely packed papillae. Organs characterized by less condensed parts, with or without papillae, accompany large, white, actinomorphic corollas, strong fragrances, and nocturnal presentation, perhaps to round out an attractive combination of traits for bats (e.g., Ayensua uaipanensis, Puya aristeguie-tae). Those taxa equipped with stigmas bearing lanceolate, still more loosely folded lobes free of papillae supposedly also produce small, diurnal, white, yellow to green owers attractive to bees (e.g., Brocchinia steyermar-kii, Lindmania guianensis, Deuterocohnia longipetala, Pitcairnia brevicaly-cina).

Varadarajan and Brown further proposed that the degree of lobe compaction and the disposition of the papillae reveal oral syndromes more reliably than does gross stigma shape. Petal scales and septal nectaries also help identify targeted fauna by providing information on the quantities of nectar produced and its mode of presentation (Fig. 3.1A,B). Bernardello et al. (1991) examined a variety of Argentinian Pitcairnioideae to identify the plant characteristics responsible for the attentions of certain kinds of ower visitors. Nectary structure and the composition of secretions were emphasized. Their conclusions, several con rmed in nature, sometimes contradicted those of Varadarajan and Brown, as indicated below.

Was this article helpful?

0 0

Post a comment