Plant species decline due to abandonment of meadows cannot easily be reversed by mowing. A case study from the southern Alps

Abstract. We resumed mowing in two plots of ca. 100 m² in an abandoned meadow dominated by Brachypodium pinnatum on the slope of Monte Generoso (Switzerland). We monitored species composition and hay yield using point quadrats and biomass samples. Species frequencies changed little during 10 yr (1988–1997) while hay yields showed large fluctuations according to mean relative humidity in April-June. We performed a seed-addition experiment to test whether the establishment of meadow species is limited by lack of diaspores or favourable microsites for germination and recruitment from the seed bank. We sowed ca. 12 000 seeds of 12 species originating from a nearby meadow individually in plots of a 4 × 6 unbalanced Latin square with four treatments, burning, mowing, mowing and removal of a layer of decayed organic matter, and a control. We monitored the fate of seedling individuals for 24 months. Seedlings of all species were established and survived for 12 months, 10 species survived during at least 24 months, some reached a reproductive stage. Species responded to different qualities of microsites provided by the different treatments thus required different regeneration niches. Spontaneous long-distance immigration was insignificant. We conclude that the former species composition of abandoned meadows cannot easily be restored by mowing alone because many plant species of meadows do not have persistent seed banks and immigration over distances of more than 25 m and successful establishment is very unlikely.     

Phylogenetic analysis of the aquatic Oligochaeta under the principle of parsimony

Phylogenetic relationships between five subfamilies of Tubificidae and ten other families of microdrile oligochaetes were estimated by a Wanger parsimony analysis using PAUP (Phylogenetic Analysis Using Parsimony, by D. L. Swofford). As the apomorph character state is ambiguous for some characters, different assumptions of directionality as well as deletions of some characters are tested in a number of analyses. A general pattern is evident from the study; (1) the majority of the aquatic families are members of a large monophyletic group (the order Tubificida in a somewhat restricted sense) defined by the shared possession of atria (generally with well developed external prostate glands), but the family Tubificidae is paraphyletic within this group; (2) the Enchytraeidae appear to form a second group (the Enchytraeida) together with the exclusively marine Capilloventridae and Randiellidae, all three families characterized by the anterior location of the spermathecae; (3) the Haplotaxidae are a plesiomorph family, which stands out as a branch of its own and constitutes the ancestral part of a group comprising also all the megadriles (the Haplotaxida). However, monophyly of the Haplotaxida is likely only if the haplotaxid octogonadial condition is assumed to be derived from the tetragonadial condition characterizing most microdriles, a situation not envisaged by previous authors. The implications of the parsimony method are briefly discussed.     

Patterns of species diversity on an oceanic versus a continental island mountain: a hypothesis on species diversification1

Abstract. The vegetation on a wet mountain slope on Haleakala (an oceanic island) is compared with that on Kinabalu (a continental island) to examine relationships between regional floristic richness and α- and β-diversities. The two mountains are similar in their constant tropical climate, generic and family-level floristic elements and geological age of the summit regions, but different in regional floristic richness (rich on Kinabalu vs. poor on Haleakala). α-diversity of canopy and subcanopy tree species was much higher on Kinabalu than in comparable zones on Haleakala. Average turnover rate of species (as logarithmic community similarity) on the slope was one order of magnitude greater on Kinabalu than on Haleakala (0.127 vs. 0.017 per 100 m alt.). While there were genera with wide altitudinal ranges on both mountains, a large proportion of the genera was differentiated into parapatric altitudinal congeners on Kinabalu. By contrast, most genera are altitudinally monotypic on Haleakala. The number of sympatric congeners per genus, and the frequency of multi-specific genera per plot were high on lower slopes but decreased with increasing altitude on Kinabalu, whereas the values were low across all altitudes on Haleakala. These patterns suggest that sympatric and parapatric species radiation was less on Haleakala than on Kinabalu. This may be related to Haleakala's initially poor and disharmonic flora.     

Pupation site choice of a North American lycaenid butterfly: the benefits of entering ant nests

Abstract.

• 1 Larvae of the North American lycaenid butterfly Hemiargus isola Reakirt tended by the ant Formica perpilosa Wheeler often enter nests of this ant species, and pupate in tunnels and chambers near the surface. Untended larvae and those tended by the ants Dorymyrmex Forel sp. (smithi complex), Forelius foetida (Buckley), and Myrmecocystus mimicus Wheeler pupate in crevices in the ground, under bark, and on leaves; but rarely inside ant nests.
• 2 The location and structure of F.perpilosa nests facilitates discovery by H.isola prepupae. At the southeast Arizona study site, F.perpilosa nests are located at the base of H.isola's host plant, whereas other species’nests are in open ground. Also, F.perpilosa nest openings are wide, whereas those of other species may be too narrow for prepupae to enter.
• 3 Prepupae associated with F.perpilosa spent 67% less time on the ground searching for pupation sites than prepupae associated with other ant species. Pupae in artificial chambers connected to F.perpilosa nests were 4–5 times less likely to disappear overnight, presumably due to predation, than those not connected to nests.
• 4 Formica perpilosa ants tend pupae inside nests. However, in the laboratory experiments tended pupae did not lose more weight prior to eclosion than untended ones, suggesting that chemicals or sounds produced by pupae as ant attractants are inexpensive, or are produced whether or not ants are present.
• 5 Newly-eclosed butterflies exited nests unmolested by ants in the field, but were attacked if confined with ants for several minutes after eclosion in the laboratory.

     

Phylogeny and cladistic classification of terrestrial nemerteans: the genera Pantinonemertes Moore & Gibson and Geonemertes Semper

Evolutionary relationships among seven species from two genera ( Pantinonemertes and Geonemertes ) of terrestrial nemerteans (phylum Nemertea) were estimated by a Wagner analysis of 27 morphological, ecological and life history characters. Pantinonemertes was found to be a paraphyletic taxon, and it is suggested that this genus should be combined with Geonemertes to form a monophyletic group. A previous hypothesis for how terrestrial nemerteans evolved is discussed and compared to the results of the cladistic analysis. This suggests that terrestrial and semi-terrestrial species evolved from a marine ancestor; the upper littoral and marine environments have been recolonized by descendants from a terrestrial ancestor.     

我国六种新蚤雄性阉割描记及关于单齿新蚤的商榷(蚤目：多毛蚤科)

在所收藏的蚤类标本中,查出新蚤属6种、亚种2,例雄性阉割畸形,其中阿巴盖新蚤Neopsylla abagaitui 3例,二卤新蚤N,btdentatiformis 9例,类新蚤N.Compar 1例,近代新蚤东方亚种N.Pleskei orientalis 4例,鞍新蚤N.Sellaris 7例,特新蚤指名亚种N.S,specialis 1例。 这些标本获自黑龙江,吉林、内蒙古,宁夏、甘肃、河北和云南。本文对畸形蚤形态进行了描述。分析关于单齿新蚤 Neopsylla monodcntattformis Huang ct Xic,1987的原始描述和形态特征图,认为其鼓名模式可能系二齿新蚤畸形标本,那么其种名将成为国际动物命名法规拒绝的名称。     

Recent mathematical approaches to reconstruct phylogenies: A chemosystematist's and botanist's view

Some basic problems of mathematical phylogenetics are discussed. While algorithms regularly depend on the principle of parsimony, some features of phylogenesis interfere with that principle. Nonrandomness of the distribution of mutations as well as the inconstancy of the molecular clock in time and within a given sequence can bias the calculated relationships of closely related taxa. True comparability of sequences is difficult to establish, since this requires defining of homology of positions and of functions of amino acids as well. Parallelism and convergence can give rise to errors in establishing homology. Furthermore, they are difficult to be integrated into a consistent mathematical approach. The asymmetry of identity versus difference matrices is discussed. Common mathematical procedures implicate the monophyletic hypothesis as well as strict dichotomy of the final tree. Real phylogeny demands to introduce more flexible approaches with respect to monophyly and dichotomy. Graph theory offers the possibility to prove the minimality of a given tree and to develop more flexible approaches. The consequences of altering the procedures to compare sequences can be tested. This is demonstrated by calculations with a set of 15 cytochromes from various taxa. To interpret a calculated tree requires a sharp distinction between taxonomy and phyletics. This is exemplified for the case of directly linked taxa. The limits of resolving uncertain relationships by accumulating more data are mentioned.This paper was partly presented at the Symposium Theory and practice of botanical classification, during the 14th International Botanical Congress, Berlin, July 1987.     

Ecosystem development on Hawaiian lava flows: biomass and species composition

Abstract. The strong environmental gradients and ‘natural experimental design’ of Mauna Loa volcano, Hawaii, provide an outstanding opportunity to study controls on ecosystem development. We measured above-ground vascular plant biomass and species composition on 42 sites on which precipitation, temperature, substrate texture, and substrate age varied substantially and largely independently. Biomass and species richness of live plants were strongly correlated with precipitation and lava flow age, but not with temperature or lava flow texture. Species composition, as measured by correspondence analysis, was likewise correlated with precipitation and flow age, but composition was also strongly influenced by temperature. Lava texture had a complex effect on vegetation, with ‘a’ a lava favoring vegetation development on wet sites and pāhoehoe favoring development on dry sites. Many locations remain virtually free of invasion by alien species; aliens appear where disturbance has facilitated invasion, either from stand-level dieback in rainforest or a grass-fire cycle on the dry, leeward side of the mountain. All four of the environmental factors studied here (precipitation, temperature, substrate texture, and substrate age) exert significant and independent control over vegetation biomass and/or species composition on Mauna Loa.     

The application of electrophoresis to the systematics of the marine dinoflagellate genus Heterocapsa

Eight strains (and three subcultures of one strain) of four species of the marine dinoflagellate genus Heterocapsa (H. illdefina, H. niei, H. pygmeea, and H. triquetra) were assayed electrophoretically for enzymes encoded by four loci. Additionally, electromorphs of the peridinin-chlorophyll a-protein pigment complex were investigated. A roote Wagner tree was constructed and indicates evolutionary lines of descent, as well as the degree of relatedness between subcultures, isolates, and taxa. There was a correlation between the degree of geographical isolation and taxonomic distance as determined from electrophoresis. Minor electrophoretic differences were detected among four subcultures of H. pygmaea that were prepared 25 years ago. The present morphologically derived classification of this genus agrees with our biochemically based systematic scheme with one exceptin. One of the isolates previously identified as H. pygmaea is considered an undescribed, possibly sibling species.