Fine‐ and Broad‐Scale Approaches to Understanding the Evolution of Aggression in Crickets

Male field crickets frequently engage in agonistic contests to establish dominance in social interactions and gain access to mate attraction territories. Crickets (Orthoptera: Gryllidae) are often used as a model taxon to study aggression, but limited documentation of aggression in some cricket species hinders our understanding of its evolutionary costs and benefits. Our study investigated cricket aggression at two scales: the within‐species scale for two cricket species, Gryllus assimilis and G. veletis, whose aggression had not been adequately documented and the among‐species scale to detect evolutionary patterns in species’ levels of aggression. In both G. veletis and G. assimilis, winners spent more time being aggressive than losers, but they were not larger or heavier. Collectively, our results reveal that G. veletis males are more aggressive than G. assimilis. Male G. veletis had higher aggression scores that male G. assimilis. The majority of G. veletis contests escalated to grappling (a highly aggressive behavior), while less than one quarter of G. assimilis contests escalated to grappling. Further, G. veletis males transitioned between two of the most aggressive behaviors most often while G. assimilis transitioned between two of the least aggressive behaviors most often. We integrate this new information on aggression for G. assimilis and G. veletis with previously documented aggression data for many cricket species to investigate aggression in a broader evolutionary context than previously possible. Within a phylogenetic context, we test the hypothesis that species whose males use burrows from which to call and attract females are more aggressive than species with non‐burrowing males. We found evidence consistent with this hypothesis; species with burrowing males tended to be more aggressive than species with non‐burrowing males. Together, our study provides fine‐scale understanding of aggression in two cricket species and broad‐scale evolutionary context for aggression across cricket species.     

The effect of density on aggression between a highly invasive and native fish

Population densities of invasive species fluctuate spatially and temporally, suggesting that the intensity of their aggressive interactions with native species is similarly variable. Although inter‐specific aggression is often thought to increase with population density, it is often theorized that it should be exceeded by intra‐specific aggression since conspecifics share a greater degree of resource overlap. Yet, the magnitude of intra‐specific aggression is seldom considered when examining aggressive interactions, particularly those between invasive and native species. Here, we manipulated the density of the invasive eastern mosquitofish, Gambusia holbrooki, and observed its aggressive interactions with juveniles of the native Australian bass, Macquaria novemaculeata in a laboratory setting. For both species, the magnitudes of intra‐ and inter‐specific aggression were recorded. Regardless of density, the native M. novemaculeata was more aggressive towards heterospecifics than G. holbrooki was. In addition to this, M. novemaculeata was more aggressive to G. holbrooki than towards conspecifics, at both low‐ and high‐density conditions. In contrast, G. holbrooki was similarly aggressive towards M. novemaculeata and G. holbrooki at a high density, yet at low density, displayed significantly more aggression towards conspecifics than M. novemaculeata. These findings demonstrate the importance of considering intra‐specific aggression when exploring behavioural interactions between native and invasive species.     

A Comparative Study of Agonistic Behaviour in Hairy-footed Gerbils (Genus Gerbillurus)

Intraspecific agonistic behaviour was investigated by means of staged encounters in Gerbillurus paeba paeba, G. p. exilis, G. tytonis, G. setzeri and G. vallinus. Four groups of behaviour were identified by motivational analysis: i.e. “exploratory and solitary”, “aggressive”, “submissive”, and “sexual” behaviour. Frequencies of acts and levels of interaction differed among species and sexes. Cluster analysis of behaviour data revealed three clusters which agree partially with the karyology and taxonomy of the genus. G. p. paeba and G. tytonis were very aggressive and highly active; female G. p. exilis and G. setzeri less so; while male G. p. exilis and G. vallinus were least aggressive and active, performing more contact-promoting behaviour than other species. A range of social types is exhibited from solitary (G. p. paeba and G. tytonis) through semi-tolerant (G. setzeri and female G. p. exilis) to tolerant (male G. p. exilis and G. vallinus).     

Male-Female Interactions in Hairy-footed Gerbils (Genus Gerbillurus)

Staged 10-min encounters between male and female gerbils of the same species were characterized by high levels of exploratory and solitary behaviour, variable levels of agonistic behaviour, and little contact-promoting behaviour. Female Gerbillurus paeba paeba, G. p. exilis and G. tytonis dominated males of these species, while male and female G. setzeri and G. vallinus were equally aggressive. Results of this study indicate that G. p. paeba, G. p. exilis and G. tytonis are aggressively solitary and that females behave aggressively towards unfamiliar males, while G. setzeri and G. vallinus are more tolerant. This is in partial agreement with findings for other gerbil species.     

Assemblages of sea stars (Echinodermata: Asteroidea) and brittle stars (Echinodermata: Ophiuroidea) in the Weddell Sea (Antarctica) and off Northeast Greenland (Arctic): a comparison of diversity and abundance

Composition and distribution of asteroid and ophiuroid assemblages were investigated by means of Agassiz trawl catches at 34 stations in 220- to 1,200-m depth in the Weddell Sea and at 17 stations in 90- and 830-m depth off Northeast Greenland. A total of 86 species (48 sea stars, 38 brittle stars) were identified in the Weddell Sea whereas off Northeast Greenland a total of 26 species (16 sea stars, 10 brittle stars) were recorded. In both study areas, brittle stars were numerically more important than sea stars, and abundances generally decreased with water depths. Multivariate analyses revealed a conspicuous depth zonation of sea and brittle stars off Greenland. Very high abundances of Ophiocten sericeum and Ophiura robusta characterized the assemblages on shallow shelf banks whereas in greater depths Ophiopleura borealis, Ophioscolex glacialis and Ophiacantha bidentata became dominant, albeit at significantly lower densities. Mass occurrences of brittle stars, such as those recorded on Greenlandic shelf banks, have not been discovered in the Weddell Sea, where distinct assemblages were discriminated in deep shelf trenches as well as on the eastern and southern shelf. Ophioplocus incipiens, Ophiurolepis martensi and Ophiurolepis brevirima were the most prominent species on the eastern shelf. Ophiacantha antarctica, Ophiurolepis gelida and Ophionotus victoriae on the southern shelf, and Ophiosparte gigas as well as the asteriod Hymenaster sp., in the shelf trenches. Overall, the Weddell Sea housed conspicuously more asterozoan species than the waters off Greenland. Higher species diversity was also evident at both a regional and local scale, especially for the eastern Weddell Sea shelf. However, because many species from the Weddell Sea are closely related, the Weddell Sea assemblages were not significantly different from the Greenland ones in terms of taxonomic diversity and distinctness. Received: 29 April 1996/Accepted: 10 June 1996     

Aggressive interactions between the invasive Rio Grande cichlid (Herichthys cyanoguttatus) and native bluegill (Lepomis macrochirus), with notes on redspotted sunfish (Lepomis miniatus)

The Rio Grande cichlid (Herichthys cyanoguttatus) has been established in the Greater New Orleans Metropolitan area for at least 20 years, and its effect on native fishes is unknown. Behavioral trials were performed to determine if aggressive interactions occur between invasive H. cyanoguttatus and native bluegill (Lepomis macrochirus). When defending a territory as the resident, L. macrochirus were markedly aggressive, averaging 11.6 aggressive actions per 10-min behavioral trial. In contrast, L. macrochirus were extremely passive as invaders, with 0.5 aggressive actions per trial. Herichthys cyanoguttatus were equally aggressive as residents and as invaders, averaging 4.9 and 6.0 aggressive actions per trial, respectively. Herichthys cyanoguttatus interacted aggressively with native species whether they held territory or not, indicating that this invasive species may have fundamentally different strategies of aggression compared with native L. macrochirus. These differences may explain the continued success of H. cyanoguttatus as an invasive fish in southeastern Louisiana.     

中国腹枝衣属地衣的多样性与区系研究

为探讨中国腹枝衣属地衣的物种多样性,进一步明确其分布特征与种类组成,该研究通过野外调查及采集地衣标本,结合形态、解剖、化学等方法,对128份采自中国热带及亚热带地区多个省份的腹枝衣属(Herpothallon)地衣标本进行了分类鉴定,共鉴定出腹枝衣属地衣12种,其中南方腹枝衣 [H. australasicum (Elix)Elix & G. Thor]、颗粒腹枝衣(H. granulosum Jagadeesh Ram & G. P. Sinha)、喜马拉雅腹枝衣(H. himalayanum Jagadeesh & G. P. Sinha)、裂芽腹枝衣(H. isidiatum Jagadeesh Ram & G. P. Sinha)和小腹枝衣(H. minutum Jagadeesh)为中国新记录种。并且对该属所有已知(已报道和本次鉴定)种类进行综合分析。结果表明:(1)中国已知腹枝衣属地衣14种,占世界已报道种类的29.17%。(2)地理成分有5种类型,即泛热带分布、热带亚洲至热带澳大利亚分布、热带亚洲和热带美洲间断分布、热带亚洲分布和中国特有分布。(3)中国腹枝衣属地衣主要分布在海拔300～2 500 m的范围内。(4)生长基物多为树皮,叶生、石生和藓生的物种较少。该研究结果表明,中国南方腹枝衣属地衣的物种多样性较高,这对明确中国该属地衣物种组成以及地衣多样性保护具有重要意义。     

THE FUNCTION OF CALL ALTERNATION IN ANURAN AMPHIBIANS: A TEST OF THREE HYPOTHESES

Males of many species of anurans alternate calls with those of their neighbors in a chorus. This pattern of calling reduces signal interference and may: 1) facilitate intermale spacing because males can better gauge the intensity of neighbors' calls if these calls do not overlap with their own; 2) help preserve species-specific temporal information in calls required to attract females; and/or 3) make it easier for females to localize males in the chorus. I tested these hypotheses with three species that exhibit call alternation, Hyla crucifer, H. versicolor, and H. microcephala. Males of all three species gave more aggressive calls to high-intensity synthetic stimuli that alternated with their calls than to those that overlapped their calls. These results support the first hypothesis. Results of four-speaker female choice experiments using alternating and overlapping calls indicate that preservation of signal integrity also is important in H. versicolor and H. microcephala, species that have fine-scale temporal information in their calls. However, the third hypothesis was not supported; females failed to discriminate among alternating and overlapping calls if the problem of signal disruption was eliminated or irrelevant.     

Fecundity and feeding of <Emphasis Type="Italic">Galerucella calmariensis</Emphasis> and <Emphasis Type="Italic">G. pusilla</Emphasis> on <Emphasis Type="Italic">Lythrum salicaria</Emphasis>

Fecundity and feeding of two introduced sibling biological control species, Galerucella calmariensis and G. pusilla (Coleoptera: Chrysomelidae) on purple loosestrife, Lythrum salicaria L. (Lythraceae) were compared at constant temperatures of 12.5, 15, 20, 25, and 27.5 °C. Larval feeding was also carried out at 30 °C, but at this temperature, larvae developed only to the L2 stage and none pupated. Thus, data for this temperature were not used in the analysis. There were significant species × temperature interactions in fecundity. Of the two species, Galerucella pusilla laid more eggs. Although egg production of both species was lowest at 12.5 °C and increased to 20 °C, at higher temperatures, the two species reacted differently. From 25 to 27.5 °C, egg production decreased for G. pusilla, but G. calmariensis fecundity peaked at 27.5 °C. Significant temperature × species × life-stage interactions were also observed in feeding. For each species, the amount of feeding varied with temperature and stage of development. Galerucella pusilla adults consumed more foliage at 15, 20, and 27.5 °C. However, at 12.5 °C G. calmariensis adults fed more than G. pusilla. G. pusilla larvae consumed an average of 25% less foliage than G. calmariensis. The lower larval consumption of G. pusilla suggests that when food is limited, G. pusilla larvae may have a higher survival rate because of its ability to complete larval development with less food and produce more progeny due to its greater fecundity. When food is not limited neither species would have a competitive advantage and both species could coexist temporally and spatially. However, since G. calmariensis larvae consumed more leaf material, the larval stage of this species would have a greater impact on purple loosestrife than G. pusilla.     

The Role of Wing Coloration in Sex Recognition and Competitor Recognition in Rubyspot Damselflies (Hetaerina spp.)

The decision rules that animals use for distinguishing between conspecifics of different age and sex classes are relevant for understanding how closely related species interact in sympatry. In rubyspot damselflies (Hetaerina spp.), the red wing coloration of mature males is hypothesized to be a key trait for sex recognition and competitor recognition within species and the proximate trigger for interspecific male–male aggression. We tested this hypothesis by manipulating the wing coloration of tethered conspecific intruders and measuring the responses of territory holders of three species in the field. As predicted, covering the red spots of mature males with black ink nearly eliminated territorial responses, and in some cases, territorial holders clasped the blackened males as if they were females. Adding red spots to female wings triggered territorial responses and nearly eliminated sexual responses. Immature males with artificial red spots were attacked at the same rate as mature male intruders, and much more frequently than were immature male controls. The results varied somewhat by species. In H. titia, the only species of Hetaerina with substantial black wing pigmentation, the effects of blackening the red spots of intruders varied both geographically and seasonally. But even when blackening the red spots of male intruders did not reduce the aggressive response of H. titia territory holders, adding artificial red spots to female wings elicited aggressive responses and nearly eliminated sexual responses. The results of this study further strengthen the evidence that interspecific aggression in Hetaerina results from overlap in territorial signals and that the derived black wing pigmentation of H. titia reduces interspecific aggression.     

Aggressive Behaviour Between Gymnocharacinus Bergi (Pisces, Characidae) And Other Neotropical Fishes From A Thermal Stream In Patagonia

Gymnocharacinus bergi is a stenothermal endangered fish only found in the headwaters of a thermal stream within the temperate Somuncurá Plateau (Patagonia, Argentina). In spite of the presence of other fish species in the Valcheta Stream basin, none of these has been found at the headwaters. Temperature and salinity cannot account for the absence of extremely eurytopic Cnesterodon and Jenynsia. In addition, there is no evidence of diet overlapping or territory defence between these species and G. bergi. Therefore, we hypothesise that agonistic behaviour might be related to G. bergi's isolation. Experiments were performed in order to analyse interspecific interaction between G. bergi and individuals of the other two species. Cnesterodon decemmaculatus showed a submissive behaviour while Jenynsia multidentata was clearly aggressive. G. bergi decreased its aggressive behaviour towards C. decemmaculatus throughout the experiment. However, when placed with J. multidentata, its aggressive behaviour did not diminish. We suggest that the characteristics of the agonistic behaviour displayed by J. multidentata, opposite from those displayed by C. decemmaculatus, might account for the absence of J. multidentata in G. bergi's present habitat. With respect to C. decemmaculatus, other factors such as its low counter current swimming ability might play a major role in this phenomenon.     

Tooth Size Variation in Assemblages of Tremacyllus (Hegetotheriidae,Notoungulata): Insights into Geographical Gradients,Systematics, and Sexual Dimorphism

Tooth size variation within fossil assemblages can be associated with intra- or interspecific variation, functional, developmental, and geographical factors, and/or sexual dimorphism. Understanding these sources of variation is necessary to develop diagnoses for fossil mammals, where teeth are usually the most frequent remains. Tremacyllus (Ameghino, 1891) (Hegetotheriidae, Notoungulata) is a genus of small-sized herbivorous mammals abundant in late Miocene to Pliocene outcrops of southern South America. Its simplified, euhypsodont dentition and size variability have hampered systematics studies and led, for instance, to an overestimation of the number of species. I analyzed tooth size variations within assemblages of Tremacyllus in a quantitative framework to test three hypotheses: (1) magnitudes of size variation are different among tooth loci and assemblages; (2) tooth size follows a geographical pattern within the analyzed sample (Bergmann’s rule), but is also associated with taxonomy; and (3) there is a correlation between size variation and sexual dimorphism reflected in distinguishable subgroups. Results indicate that patterns of variation might be associated with eruption time and/or functional position. Northwestern forms are larger than southwestern-Pampean ones, not conforming to Bergmann’s rule but revealing a strong influence of latitude. Size differences between assemblages agree with dental features that distinguish T. incipiens and T. impressus, allowing expanded species diagnoses. Two size subgroups might reflect sexual dimorphism in the absence of biostratigraphic or morphological differences between them. This interpretation indicates that northwestern specimens referred to T. diminutus should be referred to T. incipiens.

     

SYSTEMATICS OF THE GRACILARIACEAE (GRACILARIALES,RHODOPHYTA): A CRITICAL ASSESSMENT BASED ON RBCL SEQUENCE ANALYSES1

Generic concepts in the economically important agarophyte red algal family Gracilariaceae were evaluated based on maximum parsimony, Bayesian likelihood, and minimum evolution analyses of the chloroplast‐encoded rbc L gene from 67 specimens worldwide. The results confirm the monophyly of the family and identify three large clades, one of which corresponds to the ancestral antiboreal genera Curdiea and Melanthalia, one to Gracilariopsis, and one to Gracilaria sensu lato, which contains nine distinct independent evolutionary lineages, including Hydropuntia. The species currently attributed to Hydropuntia comprise a single well‐supported clade composed of two distinct lineages. The two most basal clades within Gracilaria sensu lato deserve generic rank: a new genus centered around G. chilensis Bird, McLachlan et Oliveira and G. aff. tenuistipitata Chang et Xia and a resurrected Hydropuntia encompassing primarily Indo‐Pacific (G. urvillei [Montagne] Abbott, G. edulis [S. Gmelin] P. Silva, G. eucheumatoides Harvey, G. preissiana [Sonder] Womersley, and G. rangiferina [Kützing] Piccone) and western Atlantic species (G. cornea J. Agardh, G. crassissima P. et H. Crouan in Mazé et Schramm, G. usneoides [C. Agardh] J. Agardh, G. caudata J. Agardh, and G. secunda P. et H. Crouan in Mazé et Schramm). Cystocarpic features within the Gracilaria sensu lato clades appear to be more phylogenetically informative than male characters. The textorii‐type spermatangial configuration is represented in two distinct clusters of Gracilaria. The rbc L genetic divergence among the Gracilariaceae genera ranged between 8.46% and 16.41%, providing at least 2.5 times more genetic variation than does the 18S nuclear rDNA. rbc L also resolves intrageneric relationships, especially within Gracilaria sensu lato. The current number of gracilariacean species is underestimated in the western Atlantic because of convergence in habit and apparent homoplasy in vegetative and reproductive anatomy.     

The meek inherit the earth: less aggressive wild mice are more successful in challenging situations

Numerous studies have shown an association between aggressiveness and several other behavioural traits. For example, more aggressive animals were bold and active explorers tending to form persistent routines whereas less aggressive animals were shy, careful but more flexible. While the former are thought to be more successful under stable conditions the latter should have advantages in more dynamic situations. These differences can apply not only to individuals but also to populations, species or groups of species with important implications to species distributions and speciation rates. Here we utilized the Morris water task (MWT) to investigate how two subspecies, Mus musculus musculus and M. m. domesticus, known to differ in aggressiveness, cope with stressful situations. We found that less aggressive musculus males performed significantly better in solving the MWT than more aggressive domesticus males. This suggests that M. m. musculus is more flexible and could be more successful under stressful and/or dynamic situations typical of dispersal bouts. It seems plausible that this difference may have had an influence on the secondary contact between musculus and domesticus populations in the past and perhaps still can affect the dynamics of the European hybrid zone between the subspecies. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113 , 310–319.     

Net design for selective control of the “plague minnow” Gambusia holbrooki that minimises impact on native Australian fishes

Gambusia holbrooki is one of the world's most environmentally damaging introduced species, being notoriously difficult to control once established. A composite double-winged fyke net comprising four vertically stacked compartments was developed to determine the potential to control G. holbrooki, while reducing negative interactions of this aggressive species with small threatened fishes. The stacked fyke net captured three times as many G. holbrooki as a conventional fyke net while maintaining consistent catches of native fishes relative to that from a conventional fyke net, and detected species-specific vertical distributions. This stratified net design represents a valuable management option for controlling this agonistic species or for limiting antagonistic interactions between G. holbrooki and native species during typical fyke sampling of native ecosystems.     

COMPETITION AND THE EVOLUTION OF AGGRESSIVE BEHAVIOR IN TWO SPECIES OF TERRESTRIAL SALAMANDERS

The effects of competition on the evolution of interspecific interference mechanisms were studied by comparing the aggressive behavior of two terrestrial salamander species from two localities that differ in the intensity of interspecific competition. Plethodon jordani and P. glutinosus are closely related, ecologically similar species that are sympatric at intermediate elevations in the southern Appalachian Mountains. Previous removal and transplant experiments showed that interspecific competition is more intense in the northeastern Great Smoky Mountains, where the species are narrowly sympatric, than in the nearby Balsam Mountains, where sympatry is broader. In laboratory encounters, P. glutinosus from the Great Smoky Mountains were more aggressive to heterospecific and conspecific intruders than were P. glutinosus from the Balsam Mountains. For P. jordani, however, the variation in interspecific and intraspecific aggressive behavior among individuals within populations was as great as the variation between populations. Alpha-selection (i.e., improved competitive ability by the acquisition of interspecific interference mechanisms) has occurred in populations of P. glutinosus under conditions of intense interspecific competition. The evolution of aggressive behavior appears to have been influenced by the intensity of intraspecific competition as well.     

Review of the East Asian species of the genera Hybrizon Fallén and Ghilaromma Tobias (Hymenoptera: Ichneumonidae: Hybrizontinae)

East Asian species of the genera Hybrizon and Ghilaromma are reviewed. Four species of Hybrizon, H. buccatus (Brébisson 1825), H. ghilarovi Tobias, 1988, H. juncoi (Ceballos 1957) and H. flavofacialis Tobias, 1988 and two species of Ghilaromma, G. orientalis Tobias, 1988 and G. ussuriensis Tobias, 1988, were recognized. H. ghilarovi was recorded from Korea, Japan and China, while H. juncoi was recorded from Korea, for the first time. The specimens recorded from Japan as G. fuliginosi (Wilkinson, 1930) by Watanabe (1984) are referred to G. orientalis herein. This species is newly recorded from Korea and Japan. Keys to East Asian species of Hybrizon and the world species of Ghilaromma are also provided.     

SYSTEMATICS OF GRATELOUPIA FILICINA (HALYMENIACEAE,RHODOPHYTA), BASED ON rbcL SEQUENCE ANALYSES AND MORPHOLOGICAL EVIDENCE,INCLUDING THE REINSTATEMENT OF G. MINIMA AND THE DESCRIPTION OF G. CAPENSIS SP. NOV.1

Grateloupia filicina (C. Agardh) Lamouroux, originally described from the Mediterranean Sea, has long been considered a textbook example of a marine red alga with a cosmopolitan distribution. An rbcL‐based molecular phylogeny, encompassing samples covering the entire geographic distribution of the species, revealed a plethora of “cryptic” species, whereby the presence of genuine G. filicina is limited to the Mediterranean basin. The phylogeny revealed a strong biogeographic imprint, with specimens from temperate regions resolved in clades composed of species inhabiting the same geographic region. Presence of widely divergent morphologies in the temperate clades indicated that several lineages have converged independently to a G. filicina‐type morphology. Tropical representatives are resolved in a single clade with very uniform G. filicina‐type morphology and pairwise sequence divergences that are lower than the average divergence observed in temperate lineages. This, combined with a lack of clear geographic structure among the tropical lineages, may indicate a more recent divergence with long‐range dispersal capacities. Violations to the biogeographic signal in temperate lineages seemed to be due to either inadequate taxonomy or recent introductions. Grateloupia minima P. & H. Crouan, a taxon placed in synonymy under G. filicina, is reinstated as a separate species distributed in the northeast Atlantic Ocean. Grateloupia capensis sp. nov. is described to accommodate specimens from South Africa with a G. filicina‐type morphology, and G. filicina var. luxurians is elevated to species status. Morphological and anatomical characters were put forward that support the distinctiveness of these three distinct species.     

Some generic concepts in Compositae – Gnaphaliinae

The species of Gnaphalium, Helichrysum and related genera in southern Africa have been surveyed and a number of groups of allied species detected in which the ratio of female to hermaphrodite flowers ranges from a majority of female to a majority of hermaphrodite and in some groups there are even homogamous species. Thus, the failure of the old sex-ratio character used to separate Gnaphalium and Helichrysum is confirmed. The validity of these groupings has been tested by studying detailed characters such as the structure of the stereome (whether undivided or fenestrated) and the type of achenial hair, as well as the more usual floral characters. Most of these plants have leaves with flat or revolute margins and the occasional occurrence of involute margins is taxonomically important. Gnaphalium L. (type G. uliginosum L.) has been redefined to include Amphidoxa DC. and Demidium DC. (female flowers epappose) and species with more hermaphrodite flowers then female. The stereome is undivided. Helichrysum remains a massive and highly diverse genus and includes Leontonyx Cass. The stereome is normally fenestrated and the receptacle epaleate. One or two species have paleae, but Rhynea with receptacle paleate and stereome undivided is maintained. A small group of species with undivided stereomes, centred on H. marifolium D.C., has had to be retained in Helichrysum because of the existence of linking species. Undivided stereome and subglobose achenial hairs enjoin the transfer of H. vestitum (L.) Willd. and two allies, as well as the group of species centred on H. paniculatum (Thunb.) Thunb., to Helipterum, despite the lack of plumose pappus. Edmondia Cass. (H. sesamoides (L.) Willd.) with distinctive habit, involute leaves and no close relatives in Helichrysum is reinstated. Pseudognaphalium Kirp., to which only P. oxyphyllum (DC.) Kirp. had previously been assigned, is extended to include, in its typical subgenus, Hypelichrysum Kirp. and a number of American species of Gnaphalium, as well as the African G. undulatum L. and G. oligandrum (DC.) Hilliard & Burtt, and the Asiatic G. hypoleucum DC. and G. chrysocephalum Franch. A new subgenus, Laphangium, is created to accommodate G. luteo-album L. and its allies. Achyrocline (Less.) DC. has been maintained, as is done in South America, and some African species placed under Helichrysum by Moesert 1910) are returned to it. Two new genera are recognized among gnaphalioid plants with undivided stereomes: Troglophyton (based on G. capillaceum Thunb.) with about seven species and Plecostachys (based on G. serpyllifolium Berg, and including G. polifolium Thunb.). Both genera straddle the old numerical boundary between Gnaphalium and Helichrysum. The monotypic Helichrysopsis Kirp. is maintained. Plants of gnaphalioid aspect with fenestrated stereomes necessitate a further new genus: Vellereophyton (type G. dealbatum Thunb., better known as G. candidissimum Lam.) with seven species. Eriosphaera Less, and Lasiopogon Cass, are redefined and enlarged to include species previously placed in Gnaphalium. Metalasia and Lachnospermum are redefined, with the transfer of the only large-headed species remaining in Metalasia to Lachnospermum. Two new genera are created for plants in this affinity previously misplaced in Helichrysum. Atrichantha is based on H. gemmiferum Bol. and one new species is described. Dolichothrix is established for the anomalous H. ericoides (Lam.) Pers. Ifloga is briefly investigated and it is shown that the distinction between sect. Ifloga and sect. Eutrichogyne Bentham must be based on characters of the capitulum, not just on annual versus subshrubby habit. Lasiopogon molluginoides DC. (=Comptonanthus Nordenstam) is transferred to Ifloga and the structure of the capitulum in the genus is discussed. Some earlier work on this group of plants is briefly summarized, the phytogeographical interest of the proposed arrangement is discussed and some general conclusions offered.     

Inter-specific competitors reduce inter-gender competition in Negev Desert gerbils

We examined gender-dependent competitive interactions between two nocturnal desert gerbil species, Gerbillus andersoni allenbyi and G. pyramidum, by a field manipulation experiment. The study was done in two 1-ha enclosed plots and included allopatric (only G. a. allenbyi) and sympatric (both species together) treatments. Seed trays and thermal imaging cameras were used to observe the gerbils foraging activities and aggressive interactions. We found that the negative effect of the competitively dominant species, G. pyramidum, on time spent in seed trays, and ability to control these artificial food patches, was stronger on male than on female G. a. allenbyi. Consequently, the aggression of male G. a. allenbyi towards female G. a. allenbyi was markedly reduced, indicating that the dominant species mediated competition between the genders of the subordinate species. Furthermore, this interference-mediated indirect effect was associated with a decrease in the body mass of male G. a. allenbyi and an increase in the survival of female G. a. allenbyi. We suggest that both the reduction in intra-specific aggression and the positive effect on female survival can potentially stabilize competitive interactions and promote coexistence in this small mammal community.