Seasonal Activity and Reproductive Biology of the Ground Beetle Carabus Dufouri (Coleoptera: Carabidae)

Eur. J.Entomol. 97: 329-338, 2000 ISSN 1210-5759 Seasonal activity and reproductive biology of the groundCarabus beetle dufouri (Coleóptera: Carabidae) An a M. CARDENAS and J uan M. HIDALGO Departamento de Biología Animal, Universidad de Córdoba, Avda. San Alberto Magno s/n, E-14071 Córdoba, Spain; e-mail: [email protected] Key words. Carabidae, ground beetle, Carabus dufouri, activity, reproductive biology, Iberian Peninsula Abstract. This paper concerns the life-cycle of Carabus dufouri Dejean 1829, one of the most representative species of Carabus in the south of the Iberian Peninsula. The study is based on data of the annual activity patterns in the natural habitat, on anatomical ob servations related to the sex and age of the specimens, on the reproductive condition of females and, finally, on the results of labora tory rearing experiments carried out to study the oviposition patterns and the course of development of immature stages. The results indicate that C. dufouri shows the annual rhythm of autumn breeders. However, the rhythm may also be related to the winter-breeder type ofNorth Africa. INTRODUCTION gramme designed to study the predominant annual life cy Organisms in their habitats are confronted with sea cles in meridional Europe was necessary to understand sonal fluctuations of physical and biotic factors. Conse the evolution and relationships between the different re quently, in order to survive, their development, reproduc productive rhythms of carabids. In order to fill in this lack tion period, and population dynamics have to be adapted of information we started to work on the life-cycle of Ibe to these environmental fluctuations. Adaptation of species rian carabid species (Cárdenas & Bach, 1992a, b; Cárde life cycle to the local environment involves a series of nas, 1994; Cárdenas & Hidalgo, 1995; Cárdenas et al., physiological and behavioural features, including growth 1996); we followed the criteria provided by Paarmann rate, annual number of generations, dormancy, adult lon (1975), Thiele (1977) and Makarov (1994). gevity and synchronization between the reproduction pe This paper investigates seasonal activity, age structure, riod and environmental conditions, fecundity, optional duration and survival of immature stages of Carabus du polymorphism and population dynamics (Neumann, fouri Dejean 1829. 1986). Most Central European Carabus species are “autumn- Carabid beetles are a group of insects sufficiently well- breeders” (Thiele, 1977), while the North African Cara- known as to allow the study of their life-cycles in relation bini studied are mostly “winter-breeders”, showing a to environmental factors. The copious literature published temperature-photoperiodic influence on the gonad dor on this subject in the past few years (i.e., Kurka, 1972; mancy (Paarmann, 1979b). The cycles of “autumn- Hůrka, 1973, 1986; Thiele, 1977; Paarmann, 1979a,breeders” b, and “winter-breeders” represent, respectively, 1990, 1994; Den Boer & Den Boer-Daanje, 1990), indi the northern and southern variants of a type of annual cates that the biology of carabid species respond on one rhythm characteristic of the Temperate zone, which hand to their habitat peculiarities, and on the other to ad should find their optimal display in the Mediterranean aptations evolved in their evolutionary history. ecosystems. Therefore, a series of studies have been It is generally accepted that in the Temperate zones the started on reproductive biology of the Carabus species life cycles of ground beetles are governed by annual os whose distribution area also includes the south of the Ibe cillations in climatic conditions. Also, phylogenetically rian Peninsula. closely related species show basically the same develop MATERIAL AND METHODS mental type, and in the different evolutionary trends a Species similar spectrum of reproductive rhythms can be found, suggesting a process of convergent evolution (Paarmann, According to Deuve (1994), Carabus dufouri is part of the 1979a). Thus, the conditions in each environment can re Mesocarabus Thomson, 1875 subgenus which constituted a Tyrrhenian line widely distributed in Central and South Europe, sult in the existence of a given developmental cycle, reaching the north of Africa (Morocco), and having its greatest rather than affecting its evolution (Hůrka, 1986; Cárdenas representation in the Iberian Peninsula with 3 species and 42 etal., 1996). subspecies (sensu Forel & Leplat, 1998). In spite of this diversi Most studies of this kind have been done in the Tem fication, only C. dufouri has colonized the southern Iberian re perate zone of Central Europe and some also in North Af gion to the south of the Guadalquivir River and it may be rica (Paarmann, 1975), but in transitional zones, such as considered as a replacement species of C. lusitanicus of which the Iberian Peninsula, they are scant (de los Santos et al., different subspecies occupy the rest of the Peninsular area 1985). Therefore, we considered that a research pro (Toulgoet & Lassalle, 1983). 329 Fig. 1. Climatogram of the research area for the sampling period (October 1996 to December 1997). C. dufouri may be found at very different altitudes (from low uted in the area considered. Systematic sampling was carried out altitude to 2,500 m) in open areas or in forests so it can be con at fortnightly intervals. sidered to be an eurytopic species. Anatomical observations related to the sex and age and to the The study area reproductive condition of the females The sampling was done in the Subbéticas Mountains Natural Age was determined by testing the softness of the integument Park, which is integrated into the Bética Chain of mountains and the extent of mandible wear, of the cephalic and thoracic which shape the South of the Iberian Peninsula and are a group bristles, and of the tibial spines and tarsal claws. Adults were of massifs of middle altitude (1,000-1,200 m as middle term) of placed in the following age classes: callows (or immature, with a calcarean nature that form a karstic landscape of great ecologi a very soft integument and unworn structures), young imagoes cal interest. They are surrounded by cultivated lowland (olive (with a hard integument but scarcely worn structures) and old groves). The dominant vegetation is typical of a Mediterranean imagoes (hard integument, and fairly worn structures, so that thick mixed forest, the Paeonio coriaceae-Quercetum rotundifo- they were probably over one year old). In the case of females, liae association, with a high level of degradation where bushes the gonadal stage and potential fecundity were also checked. and pastures prevail. The climate is of the Mediterranean type, Using the same criteria as Cardenas (1994), after dissecting the but with a clear Continental influence, belonging to a females, they were classified as: Mesomediterranean bioclimatic belt but, in the highest altitudes - Teneral females (T), callow beetles, which ovaries are not it may be considered as a Supramediterranean belt (Rivas- yet developed. Martínez, 1987) (Fig. 1). - Immature females (IF), young beetles, ovarioles not differ entiated. Study methods - Pre-reproductive females (PRF), maturing females, with oo Annual activity pattern cytes clearly diferentiated but without mature ova or corpora lu The annual activity pattern of C. dufouri was recorded in a tea. typical mediterranean mixed forest (La Nava, Subbéticas Moun - Gravid females (G), beetles with mature ova but without tains Natural Park, 30S UG 81 49 U.T.M. coordinates, 1,000 m corpora lutea. altitude) from October 1996 until the end of 1997, using twenty - Females ending reproduction (FER), imagoes with mature permanent pitfall traps each consisting of two concentric cylin- ova and corpora lutea. dric plastic pots (1,000 cc volume and 8 cm 0), using the out - Spent females (S), imagoes with regressed ovaria, without side of them as a container and the inside one as a recipient. mature ova, but with corpora lutea. Pitfall traps were mid-filled with a mixed solution of acetic acid The reproductive biology of C. dufouri as bait and ethanol (70°) as preservative, buried up to the top end, partially covered to avoid inundation and randomly distrib Laboratory rearing experiments were carried out in culture rooms, under different conditions of temperature, humidity and 330 Realised fecundity. This was defined as the mean number of eggs laid per female in a time period. Statistics Finally, for analyzing and comparing the results, the Mann Whitney non-parametric statistical test was applied (Zar, 1984). RESULTS Temporal activity pattern The temporal activity of adult C. dufouri is plotted in Fig. 3, showing two maxima, the first between April-June and the second between October-December. The periods of peak activity are not homogeneous due, probably, to sampling effects. When the activity for males and females are considered in isolation, their respective curves run parallel to those of the summed data, although the males start moving and peak in activity sooner than females. The sex-ratio is favourable for females independently of the time of year. The low activity periods are associated with extreme climatic conditions (winter or summer), but some specimens can be found at these times. Age-class distribution ofC. dufouri Following the criterion previously specified (see Mate rial and Methods section) anatomical studies enabled us to establish three age-classes as represented in Fig. 4. The majority of the members of the

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