@phdthesis{Berghoff2002,
  author    = {Berghoff, Stefanie M.},
  title     = {Sociobiology of the hypogaeic army ant Dorylus (Dichthadia) laevigatus Fr. Smith},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-5005},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2002},
  abstract  = {Originally renowned for their spectacular epigaeic raids, army ants have captured scientific attention for almost two centuries. They now belong to one of the best studied group of ants. However, most of our knowledge about army ants was derived from the study of the minority of specialized, epigaeicly active species. These species evolved probably rather recently from hypogaeic ancestors. The majority of army ant species still leads a hypogaeic life and is almost completely unknown in its entire sociobiology. It thus remained speculative, whether the assumed 'general' characteristics of army ants represent an adaptation to epigaeic activity or apply also to the majority of hypogaeic species. Based on the recent observation that the hypogaeic Asian army ant Dorylus (Dichthadia) laevigatus recruits predictably to palm oil baits, I developed and tested an oil-baiting method for the study of hypogaeic (army)ants. Prior to my study, nothing was known about the sociobiology of the assumed rare D. laevigatus. Throughout my work, I showed D. laevigatus to be very common and abundant in a wide range of habitats in West-Malaysia and on Borneo. Investigating its foraging behavior, I revealed D. laevigatus to differ from epigaeicly active species in several ways. Never demonstrated for any of the epigaeic species, D. laevigatus established stable trunk trail systems. Such a trail system contradicted the perception of army ant foraging, which was believed to be characterized by raids with constantly alternating trail directions. The trunk trail system further enabled a near omnipresence of D. laevigatus within its foraging area, which was also believed to be atypical for an army ant. Raids differed in structure and composition of participating workers from those of epigaeic species. Also, bulky food sources could be exploited over long periods of time. The foraging system of D. laevigatus resembled in several ways that of e.g. leaf-cutter and harvester ants. Likewise contrary to the assumptions, D. laevigatus had a wide food spectrum and showed only little effect on local arthropod communities, even falling itself prey to other ants. Strong aggressive behavior was observed only towards ant species with similar lifestyles, enabling me to provide the first detailed documentation of interspecific fights between two sympatric Dorylus species. Similar to foraging habits or ecological impact, nothing was known about colony size and composition, nesting habits, or worker polymorphism for D. laevigatus or any other hypogaeic Dorylus species prior to my work. By observing and eventually excavating a colony, I showed D. laevigatus to have a much smaller colony size and to lack the large sized workers of epigaeic Dorylus species. Similar to epigaeic Dorylinae, I showed D. laevigatus to have a non-phasic brood production, to emigrate rarely, and to alter its nest form along with habitat conditions. Detailed morphological and geographical descriptions give an impression of the Asian Dorylus species and are expected to aid other researchers in the difficult species identification. The genetic analysis of a male collected at a light trap demonstrated its relation to D. laevigatus. Confirming the male and queen associations, D. laevigatus is now one of five Dorylus species (out of a total of 61), for which all castes are known. In cooperation with D. Kistner, I provide a morphological and taxonomical description of nine Coleopteran beetles associated with D. laevigatus. Behavioral observations indicated the degree of their integration into the colony. The taxonomic position of the beetles further indicated that D. laevigatus emigrated from Africa to Asia, and was accompanied by the majority of associated beetles. The diversity of D. laevigatus guests, which included a number of unidentified mites, was rather low compared to that of epigaeic species. Overall, I demonstrated the developed baiting containers to effectively enable the study of hypogaeic ants. I showed several other hypogaeic ant species to be undersampled by other methods. Furthermore, the method enabled me to documented a second hypogaeic Dorylus species on Borneo. A detailed description of this species' morphology, ecology, and interactions with D. laevigatus is provided. My study indicated D. laevigatus to be an ecologically important species, able to influence soil structure and organisms of tropical regions in many ways. Relating the observed traits of D. laevigatus to epigaeicly active species, I conclude that our assumption of 'general' army ant behavior is erroneous in several aspects and needs to be changed. The oil-baiting method finally provides a tool enabling the location and study of hypogaeic (army)ant species. This opens a broad field for future studies on this cryptic but nonetheless important group of ants.},
  subject      = {Borneo},
  language  = {en}
}
@phdthesis{Menzel2009,
  author    = {Menzel, Florian},
  title     = {Mechanisms and adaptive significance of interspecific associations between tropical ant species},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37251},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {Aggression between ants from different colonies or species is ubiquitous. Exceptions to this rule exist in the form of supercolonies (within a species) and interspecific associations (between species). Probably the most intimate interspecific association is the parabiosis, where two ant species live together in a common nest. They keep their brood separate but jointly use trails and often share food resources. Parabioses are restricted to few species pairings and occur in South American and Southeast Asian rainforests. While the South American parabioses have been studied, albeit poorly, almost nothing is known about their Southeast Asian counterparts. My PhD project focuses on Southeast Asian parabioses between the myrmicine Crematogaster modiglianii Emery 1900 and the considerably larger formicine Camponotus rufifemur Emery 1900. The two species frequently nest together in hollow trees in the tropical lowland rainforest of Borneo. The basic question of my PhD project is why these two species live together. I investigated both proximate and ultimate aspects of this question. For comparative purposes, I included studies on a trail-sharing association in the same habitat. On the proximate level, I investigated which mechanisms facilitate tolerance towards hetero-spe¬ci¬fic nestmates. Ants generally discriminate nestmates from non-nestmates via cuticular hydro¬carbons that function as colony recognition cues. I studied the specificity of nestmate recognition within and between the two parabiotic species. Using gas chromatography-mass spectrometry (GC-MS), I analyzed the cuticular substances in both ant species to find potential differences to non-parabiotic species, and to estimate the substance overlap among the two species. A high substance overlap would e.g. suggest that interspecific tolerance is caused by chemical mimicry. Finally, bioassays were conducted to evaluate the function of different cuticular compounds. Interspecific tolerance in the two parabiotic species was species-specific but not colony-specific. Ca. rufifemur tolerated all Cr. modiglianii individuals, even those from foreign colonies, but strongly attacked workers of other Crematogaster species. Cr. modiglianii, in turn, tolerated Ca. rufifemur workers of certain foreign colonies but attacked those of others. Chemical analyses revealed two sympatric, chemically distinct Ca. rufifemur varieties ('red' and 'black') with almost no hydrocarbon overlap. Cr. modiglianii only tolerated foreign Ca. rufifemur workers if they belonged to the same chemical variety as their own Ca. rufifemur partner. It also attacked other, non-parabiotic Camponotus species. Thus, reciprocal interspecific tolerance was restricted to the species Cr. modiglianii and Ca. rufifemur. Ca. rufifemur frequently tolerated conspecific non-nestmates of the same chemical variety. Minor workers were more often tolerated than majors, possibly because they possess two to three times lower hydrocarbon quantities per body surface than majors. In contrast, Cr. modiglianii nearly always attacked conspecific non-nestmates. Both species possessed hydrocarbons with considerably higher chain lengths than congeneric, non-parabiotic ant species. Long-chain hydrocarbons are less volatile than shorter ones and thus harder to perceive. They may thus considerably facilitate interspecific tolerance. Moreover, up to 98\% of the cuticular hydrocarbons in Ca. rufifemur were methylbranched alkenes, which are highly unusual among insect cuticular hydrocarbons. Cr. modiglianii and Ca. rufifemur had almost no hydrocarbons in common, refuting chemical mimicry as a possible cause of interspecific tolerance. The only hydrocarbons common to both species were two methylbranched alkenes, which constituted 89\% of the 'red' Ca. rufifemur hydrocarbon profile and also occurred in those Cr. modiglianii colonies that lived together with this Ca. rufifemur variety. Cr. modiglianii presumably acquired these two compounds from its red Ca. rufifemur partner. Cr. modiglianii was significantly less aggressive towards foreign Cr. modiglianii workers that were associated with the same Ca. rufifemur variety than to those associated with the respective other one. Hence, this species seemed to use recognition cues acquired from its parabiotic partner. Apart from hydrocarbons, both species possessed a set of hitherto unknown substances on their cuticle. The quantitative composition of the unknown compounds varied between parabiotic nests but was similar among the two species of a nest. They are probably produced in the Dufour glanf of Cr. modiglianii and transferred to their Ca. rufifemur partner. Possible transfer mechanisms include interspecific trophallaxis and 'mounting behaviour', where Cr. modiglianii climbed onto Ca. rufifemur workers without being displaced. Although the composition of the unknown compounds greatly varied between nests, they did not function as nestmate recognition cues since both species used hydrocarbons for nestmate recognition. However, the unknown compounds significantly reduced aggression in Ca. rufifemur. The ultimate, i.e. ecological and evolutionary aspects of my PhD research deal with potential costs and benefits that Cr. modiglianii and Ca. rufifemur may derive from the parabiotic association, their interactions with other species, and population genetic analyses. Additional studies on a trail-sharing association between three other ant species deal with two possible mechanisms that may cause or facilitate trail-sharing. Whether parabioses are parasitic, commensalistic, or mutualistic, is largely unknown and depends on the costs and benefits each party derives from the association. I therefore investigated food competition (as one of the most probable costs), differentiation of foraging niches (which can reduce competition), and several potential benefits of the parabiotic way of life. Besides, I studied interactions between the ant species and the hemiepiphyte Poikilospermum cordifolium. The foraging niches of the two species differed regarding foraging range, daily activity pattern, and food preferences. None of the two species aggressively displaced its partner species from baits. Thus, interference competition for food seemed to be low or absent. For both ant species, a number of benefits from the parabiotic lifestyle seem possible. They include interspecific trail-following, joint nest defence, provision of nest space by the partner species, food exchange via trophallaxis, and mutual brood care. If an ant species follows another species' pheromone trails, it can reach food resources found by the other species. As shown by artificial extract trails, Ca. rufifemur workers indeed followed trails of Cr. modiglianii but not vice versa. Thus, Ca. rufifemur benefited from Cr. modiglianii's knowledge on food sources (informational parasitism). In turn, Cr. modiglianii seemed to profit from nest defence by Ca. rufifemur. Ca. rufifemur majors are substantially larger than Cr. modiglianii workers. Although Cr. modiglianii often effectively defended the nest as well, it seemed likely that this species derived a benefit from its partner's defensive abilities. In neotropical parabioses (ant-gardens), mutualistic epiphytes play an important role in providing nest space. The neotropical Camponotus benefits its Crematogaster partner by planting epiphyte seeds, for which Crematogaster is too small. Similarly, the Bornean parabioses often were inhabited by the hemiepiphyte Poikilospermum cordifolium (Barg.-Petr.) Merr (Cecropiaceae). P. cordifolium seedlings, saplings and sometimes larger indivi¬duals abundantly grew at the entrances of parabiotic nests. However, P. cordifolium provides no additional nest space and, apart from nutritive elaiosomes, perianths, and extrafloral nectar probably plays a less important role for the ants than the neotropical epiphytes. In conclusion, the parabiosis is probably beneficial to both species. The main benefits seem to be nest defence (for Cr. modiglianii) and interspecific trail-following (for Ca. rufifemur). However, Ca. rufifemur seems to be more dependent on its partner than vice versa. For both parabiotic species, I analyzed mitochondrial DNA of ants from different regions in Borneo. My data suggest that there are four genetically and chemically distinct, but closely related varieties of Camponotus rufifemur. In contrast, Crematogaster modiglianii showed high genetic differentiation between distant populations but was not differentiated into genetic or chemical varieties. This argues against variety-specific cocladogenesis between Cr. modiglianii and Ca. rufifemur, although a less specific coevolution of the two species is highly likely. In Bornean rainforests, trail-sharing associations of Polyrhachis (Polyrhachis) ypsilon Emery 1887 and Camponotus (Colobopsis) saundersi Emery 1889 are common and often include further species such as Dolichoderus cuspidatus Smith 1857. I investigated a trail-sharing association between these three species and studied two mechanisms that may cause or facilitate these associations: interspecific trail-following, i.e. workers following another species' pheromone trail, and differential inter¬specific aggression. In trail-following assays, D. cuspidatus regularly followed extract trails of the other two species, thus probably parasitizing on their information on food sources. In contrast, only few P. ypsilon and Ca. saundersi workers followed hetero¬speci¬fic extract trails. Hence, the association between P. ypsilon and Ca. saundersi cannot be ex¬plained by foragers following heterospecific trails. In this case, trail-sharing may originate from few scout ants that do follow heterospecific pheromone trails and then lay their own trails. Interspecific aggression among P. ypsilon, Ca. saundersi and D. cuspidatus was strongly asymmetric, Ca. saundersi being submissive to the other two species. All three species discriminated between heterospecific workers from the same and a distant trail-sharing site. Thus, it seems likely that the species of a given trail-sharing site habituate to one another. Differential tolerance by dominant ant species may be mediated by selective habituation towards submissive species, and thereby influence the assembly of trail-sharing associations.},
  subject      = {Ameisen},
  language  = {en}
}
@phdthesis{Stegmann2000,
  author    = {Stegmann, Ulrich E.},
  title     = {Brutpflege, Lebensgeschichte und Taxonomie s{\"u}dostasiatischer Membraciden (Insecta: Homoptera)},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-2365},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2000},
  abstract  = {Diese Arbeit untersucht die systematische Verbreitung der Brutpflege bei s{\"u}dostasiatischen Buckelzirpen (Homoptera: Membracidae) sowie verhaltens{\"o}kologische Aspekte dieses Verhaltens bei Pyrgauchenia tristaniopsis. Erg{\"a}nzend dazu wurden Aspekte der Taxonomie, Lebensgeschichte, Reproduktionsbiologie und Morphometrie dieser Art untersucht, deren Kenntnis f{\"u}r die Interpretation des Brutpflegeverhaltens erforderlich waren. Die Ergebnisse (1) widersprechen der starken Version der Semelparitie-Hypothese (ein Fortpflanzungsereignis pro Fortpflanzungsperiode als Voraussetzung f{\"u}r Brutpflege bei Insekten), und sie zeigen, dass (2) Brutpflege bei altweltlichen Centrotinae - entgegen fr{\"u}herer Vermutungen - keine Ausnahme ist. Außerdem konnten erstmals einige grundlegende Aspekte der Biologie eines s{\"u}dostasiatischen Vertreters der Familie Membracidae gekl{\"a}rt werden. Aufsammlungen in der bodennahen Vegetation wurden in 16 Untersuchungsgebieten in West-Malaysia und Sabah (Borneo) von 1996-1998 durchgef{\"u}hrt. Weibliche Brutf{\"u}rsorge in Form von Gelegebewachung wurde bei 11 Arten aus folgenden Gattungen gefunden: Pyrgauchenia, Pyrgonota, Hybandoides, Gigantorhabdus (Hypsaucheniini), Centrochares (Centrocharesini), Ebhul (Ebhuloidesini). Larven dieser Arten lebten in Aggregationen zusammen. Drei Arten werden neu beschrieben (Pyrgauchenia biuni, P. pendleburyi, P. tristaniopsis). Zwei nominelle Arten (P. angulata Funkhouser und P. brunnea Funkhouser) sind Junior-Synonyme von P. colorata Distant. Die Arbeiten zu Pyrgauchenia tristaniopsis fanden im unteren Montanregenwald des Kinabalu Nationalparks (Borneo) statt. Diese Art wurde nur dort gefunden (zwischen 1350 m und 1650 m {\"u}. NN), und sie war polyphag (alle Entwicklungsstadien auf 11 Pflanzenarten aus 8 Familien). Es gab f{\"u}nf Larvenstadien, deren Entwicklungszeit zusammen 63-83 Tage betrug (Embryonalentwicklung: 22 Tage). Larven lebten aggregierend und wurden von Ameisen besucht (insgesamt 4 Morphospecies). Es gab Hinweise, dass frisch geh{\"a}utete Imagines noch etwa 10 Tage in der Aggregation verblieben. Sp{\"a}testens 5 bzw. 10 Tage nach der Imaginalh{\"a}utung waren Weibchen bzw. M{\"a}nnchen zu einer Erstkopulation bereit. Bei der Paarung kletterte das M{\"a}nnchen nach der Kontaktaufnahme auf das Weibchen und blieb dort im Median 138 Sekunden sitzen (Pr{\"a}kopula), worauf eine im Median 116-min{\"u}tige Kopulation folgen konnte. W{\"a}hrend der Pr{\"a}kopula sandte das M{\"a}nnchen Vibrationssignale aus. Die Art war promiskuitiv, und manche Weibchen paarten sich w{\"a}hrend der Gelegebewachung. Das Geschlechterverh{\"a}ltnis war zum Zeitpunkt der Imaginalh{\"a}utung ausgeglichen. Die Eimortalit{\"a}t aufgrund einer Kohortenanalyse betrug 35 Prozent. Pr{\"a}datoren der Larven und Imagines waren besonders Springspinnen (Salticidae). Die Eier wurden von Brachygrammatella sp. (Trichogrammatidae) parasitiert. Eier wurden als Gelege ins Gewebe von Wirtspflanzenzweigen gelegt (Unterseite). Die Anzahl Eier pro Gelege (etwa 57) nahm mit der Bewachungsdauer des Weibchens zu. Bevorzugungen von Gelegepositionen ober- oder unterhalb bereits vorhandener Gelege waren nicht festzustellen. Im Median wurden 3-4 (1998er, 1997er Zensus) Gelege zusammen auf einem Zweig gefunden. Bei einem Wiederfangversuch legte mindestens die H{\"a}lfte aller Weibchen w{\"a}hrend ihres Lebens mindestens zwei Gelege. Zwischen Verlassen des ersten Geleges (auf dem ein Weibchen gefunden wurde) und der Oviposition ihres Folgegeleges vergingen im Median 5 Tage. Folgegelege wurden meist auf derselben Wirtspflanze wie das erste Gelege abgelegt. Der Fettk{\"o}rper vergr{\"o}ßerte sich wieder nach der Oviposition, aber noch w{\"a}hrend der Bewachung des aktuellen Geleges. Weibchen saßen 26-28 Tage lang (nach Beginn der Oviposition) auf ihrem Gelege, d.h. bis zum 5.-8. Tag nach Schlupfbeginn der Larven (die Larven schl{\"u}pften sukzessiv, erst 9 Tage nach Schlupfbeginn waren die meisten LI geschl{\"u}pft). Weibchen kehrten nach experimenteller Vertreibung vom Gelege auf dieses zur{\"u}ck. In Wahlversuchen wurde aber das eigene Gelege gegen{\"u}ber einem fremden nicht pr{\"a}feriert. Weibchen wichen bei St{\"o}rungen stets zur Seite aus und begannen ihre Suche immer mit Seitw{\"a}rtsbewegungen. Experimentell herbeigef{\"u}hrter Kontakt mit dem Eiparasitoid Brachygrammatella sp. gen{\"u}gte, um die Beinabwehr bewachender Weibchen zu erh{\"o}hen. Die H{\"a}ufigkeit von Beinbewegungen war nicht nur vom Vorhandensein eines Geleges, sondern auch von der Tageszeit abh{\"a}ngig. Gelegebewachung f{\"o}rderte das {\"U}berleben der Eier: Die Eimortalit{\"a}t stieg mit experimenteller Verk{\"u}rzung der weiblichen Bewachungsdauer an (unabh{\"a}ngig von der Gelegegr{\"o}ße). Gelegebewachung verz{\"o}gerte die Ablage von Folgegelegen, wie durch experimentelles Verk{\"u}rzen der Bewachungsdauer aktuell bewachter Gelege gezeigt wurde. Abgebrochene pronotale Dorsaldornen minderten nicht die Paarungswahrscheinlichkeit: Die H{\"a}ufigkeit kopulierender M{\"a}nnchen und Weibchen mit abgebrochenem Dorn wich nicht von ihrer jeweiligen H{\"a}ufigkeit in der Population ab. Bei 52 Prozent aller Gelege bewachenden Weibchen war der Dorsaldorn abgebrochen. Weibchen waren l{\"a}nger und schwerer als M{\"a}nnchen, und einige pronotale Merkmale (z.B. der Caudaldorn) waren ebenfalls bei den Weibchen l{\"a}nger. Dorsaldorn und Distallobus waren dagegen bei M{\"a}nnchen l{\"a}nger, und zwar bei gleicher K{\"o}rpergr{\"o}ße. Geschwister {\"a}hnelten sich besonders hinsichtlich Gewicht sowie K{\"o}rper- und Dorsaldornl{\"a}nge, was durch große Heritabilit{\"a}t, gleiche Umweltbedingungen und Inzucht erkl{\"a}rt werden k{\"o}nnte.},
  subject      = {S{\"u}dostasien},
  language  = {de}
}