Spring remigration of the monarch butterfly, Danaus plexippus (Lepidoptera: Nymphalidae) in north-central Florida: estimating population parameters using mark-recapture

Monarch butterflies [Danaus plexippus) of the eastern North American population migrate each fall from die northern U.S.A. and southern Canada to overwintering sites in Mexico and return the following spring to the southeastern U.S.A. where they lay eggs and then die. The spring remigration is the least studied phase in the annual migration cycle. We therefore conducted a mark-recapture study and examined population recolonization dynamics and residence time in a north-central Florida pasture where the monarch's milkweed host plant (Asclepias humistrata) was abundant. Beginning in late March 1995 two waves of monarchs arrived, their numbers peaked at 71 individuals by mid-April, and the butterflies disappeared in early May. After arriving, the adults remained for 3–5 days, laid eggs and then continued to migrate. We also compared population sizes and arrival times in 1994 and 1996. We found no evidence of a second spring generation, which was also consistent with the deteriorating quality of the A. humistrata plants. Individuals of the new spring generation disappear shordy after eclosion. The arriving population was approximately nine times greater in 1995 than in 1996. Our findings support two recent hypodieses: (1) the bird-like migration of the monarch butterfly in North America evolved with the northward expansion and phenology of milkweeds; and (2) monarchs appear to be migratory throughout their annual cycle of several generations. By lingering for only a short time at each milkweed patch they encounter, the old monarchs returning from Mexico locate the resurgent milkweed flora over an extensive area in the southern states. Then, within less than a month, their fresh offspring continue the migration and exploit the unfolding cornucopia of milkweeds as the spring advances northward. The more we discover about the biology of this insect, the more remarkable is its annual migratory, breeding and overwintering cycle.     

Rhynchocephalians (Diapsida: Lepidosauria) from the Jurassic Kota Formation of India

Despite their rarity today, rhynchocephalians formed a diverse Early Mesozoic clade with a comparatively good fossil record. They had a Pangaean distribution in the Late Triassic and Early Jurassic, although the Gondwanan record remains more limited than the Laurasian one. We report here on new sphenodontian material from the Jurassic Kota Formation of peninsular India. Two taxa are represented, and both are attributed to new genera. One is a relatively derived sphenodontian with a premaxillary morphology similar to that of the Late Triassic/ Early Jurassic genus Clevosaurus. The other is somewhat more primitive in its morphology, although clearly a crown-group sphenodontian. In addition, three dentary fragments and a partial maxilla signal the presence of a primitive pleurodont lepidosauromorph similar to the basal rhynchocephalians Gephyrosaurus and Diphydonto-saurus from Britain.     

The novel ‘tongue‐bite apparatus’ in the knifefish family Notopteridae (Teleostei: Osteoglossomorpha): are kinematic patterns conserved within a clade?

Osteoglossomorph fishes are unique in possessing a specialized feeding mechanism, the tongue-bite apparatus (TBA) involving the hyoid apparatus. The TBA is associated with two unique behaviour patterns - raking and open-mouth chewing - used to disable and macerate prey. The kinematics of these two behaviours was compared in two species of knifefishes (family Notopteridae): Xenomystus nigri (Gunther, 1868) and Chitala ornata (Gray, 1831) using high-speed video (250 frames s"¹). Both univariate and multivariate analyses indicated that there were significant interspecific differences in both raking and open-mouth chewing. Raking can be divided into three stages; the preparatory phase, power stroke, and recovery phase. During the power stroke posterior motion of the pectoral girdle and neurocranial elevation both appear to play a major role in prey reduction. In Xenomystus the power stroke involves significantly greater levels of neurocranial elevation (35^o) and pectoral girdle motion (38% of head length; 9.5^o) than that found in Chitala (neurocranial elevation 11^o; pectoral girdle motion 11% of head length and 5^o). Indeed, Xenomystus represents the most extreme raking behaviour of any osteoglossomorph thus far studied. Temporal displacement variables demonstrated that the power stroke in Xenomystus is significantly faster than in Chitala. Although some of the interspecific differences might be size related, these data suggest that a greater degree of difference exists in these highly specialized behaviours than previous work has demonstrated. These findings support the notion that biomechanical duplication (an additional ligament found in osteoglossomorphs) could be linked to increased functional versatility.     

Systematic and comparative anatomy of Maxillarieae (Orchidaceae), sans Oncidiinae

On the basis of floral and vegetative morphology, 63 tropical American genera have been recognized within Maxillarieae. We were able to examine anatomical material of all subtribes, excluding Oncidiinae. Stegmata with conical silica bodies occur in leaves and stems of all subtribes excluding Ornithocephalinae, and pericyclic stegmata found in roots are characteristic of Lycastinae. Lycastinae and Maxillariinae are characterized by foliar glands, foliar fibre bundles and tilosomes. Endodermal cells are U-thickened in most Zygopetalinae; O-thickened in most Lycastinae, Ornithocephalinae and Telipogoninae; variously thickened in Maxillariinae; and thin-walled in Cryptarrhena lunata . Water-storage cells varied from thin-walled to variously banded throughout Maxillarieae. Cladistic analyses using anatomical characters yielded no resolution among subtribes, illustrating that anatomical characters are of limited value in assessing relationships within this tribe.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 144 , 251–274.     

Pollen morphology and wood anatomy of the Crudia group (Leguminosae, Caesalpinioideae, Detarieae)

Pollen from all 12 and wood from 11 genera in the Crudia group have been examined using light, scanning electron and transmission electron microscopy. This group is currently of systematic interest because it is part of a tribe undergoing taxonomic revision. The pollen grains fall into four groups: (1) Oxystigma, Kingiodendmn, Gossweilerodendron, Bathiaea,.Neoapaloxylon, Stemonocoleus, Guibourlia and Prioria have pollen of a widespread and generalized cacsalpinioid type that are small to medium sized, spheroidal to prolate, tricolporate and with a perforate exine, with some variation in surface ornamentation, aperture margins and ultrastructure. (2) Crudia pollen is tricolporate, coarsely striate with a coarsely scabrate to vcrmiculate aperture membrane. (3) Augouardia is tricolporate and coarsely reticulate. (4) Hardwickia and Colophosperrnum are pantoporate and reticulate or microreticulate-rugulate. The wood of Prioria, Oxystigma, Kingiodendmn and Gossweilerodendron has diffusely arranged axial canals, and these are four genera that have recently been merged into Prioria. Bathiaea has tangentially arranged axial canals. The other genera lack normal axial canals. Crudia is distinct, with banded parenchyma and variably storied short rays, Augouardia has much less abundant axial parenchyma that is mainly scanty paratracheal and vasiccntric, Guibourtia has mainly aliform parenchyma and rays variable in height and width, and Colophosperrnum and Hardwickia have similar paratracheal parenchyma patterns, although the rays tend to be wider in the latter. Our conclusion is that the Crudia group is not monophyletic.     

Systematic and functional anatomy of seedlings in mangrove Rhizophoraceae: vivipary explained?

The hypocotyl of viviparous seedlings of mangrove Rhizophoraceae (tribe Rhizophoreae) has a common suite of anatomical features but a range of anatomical structures that may be diagnostic at the generic or even specific level. This information is summarized in the form of a dichotomous key. A common and previously unreported anatomical feature is the presence of tension wood fibres developed eccentrically in secondary xylem at the distal pole of seedlings grown in both artificial and natural conditions. These fibres are apparently the source of the mechanism whereby an initially horizontal seedling becomes erected rapidly once it is rooted distally, even though this appears to be achieved at a considerable mechanical disadvantage. The morphological result is a distinct 'hook' at the distal end of the established seedling. This mechanism allows rapid erection of a horizontally stranded seedling, such that the plumule is raised, snorkel-like, above immediate tidal influence. This may be necessary, since gas exchange through the surface of the seedling is not possible via the thick, cutinized and stomata-free epidermis of the hypocotyl. We suggest that the need to produce an elongated propagule, with this self-erecting capability favours the evolution of vivipary in these plants because it permits the earliest development of the plumule in air rather than water. The suitability of mangrove seedlings for further experimental and anatomical study is emphasized. The study also exemplifies how anatomy can be placed in a dynamic context.     

The occurrence of vertical resin canals in Keteleeria, with reference to its systematic position in Pinaceae

The variation in the number of resin canals in the secondary xylem of Keteleeria fortunei (A. Murray bis) Carrière is determined. At all levels from base to top of a tree, resin canals are absent rearer the pith, but they (sporadically) appear after a certain cambial age. In addition, the occurrence of resin canals in seven named species of Keteleeria was surveyed. It was confirmed that normal vertical resin canals do occur in the mature parts of secondary xylem, but that they may be absent in the juvenile parts of secondary xylem of stems, as well as in branches and in seedlings or saplings. Earlier investigations reporting the absence of resin canals altogether in this genus may have been misled by the use of younger (immature) specimens instead of mature stems of trees. The distribution pattern of resin canals found in Keteleeria is systematically significant because it supports a new system of classification of Pinaceae, in which Keteleeria is believed to have a close relationship with Nothotsuga.