Morphological variability in Lophyra flexuosa (Fabricius, 1787) (Coleoptera, Cicindelidae) in desert countries is affected by sexual dimorphism and geographic aspect

Abstract Lophyra flexuosa, a eurytopic tiger beetle characterized by long phenological activity, wide geographic and altitudinal distribution, and occurring in the highest number of habitats among all Cicindelidae known from North Africa, was chosen to study its geographic variation in morphology and sexual dimorphism. Here, we found significant sexual dimorphism exhibited in larger body size of females and longer mandibles in males, which can be explained by different roles of particular sexes in courtship. Moreover, we recorded significant differences in body sizes between western and eastern Maghreb populations which could suggest genetic isolation between these populations. As the species is related to habitats placed close to the water reservoirs, which in the desert countries are under significant human pressure (including climate change), we expect a reduction of habitat occupied by this taxon. Therefore, the geographic morphological variability that we observe today in the tiger beetle Lophyra flexuosa in the future could lead to speciation.

. Doğan Sarikaya et al. (2020) noted differences in shape and size of head and pronotum between males and females of tiger beetles. Rarely, sexual differences can be observed also in the coloration of the body (Kippenhan, 1997;Pearson & Vogler, 2001) or only some parts of body are differently colored, for example, prothoracic tarsal pads (Palmer, 1981) or mandibles (Cassola & Bouyer, 2007;Pearson, 1988), which in the case of males are usually white, while in females they are darkly colored. Moreover, like all other Adephaga beetles, males of almost all tiger beetle species have ventral surfaces of the three to four tarsal segments of the first pair of legs, thickly covered with pads of setae, which is an adaptation to grasp and hold females during copulation (Stork, 1980). The tiger beetle, Lophyra flexuosa (Fabricius, 1787), is widely distributed in western Palearctic, occurring from the Iberian Peninsula and Morocco in the west to Middle Asia in the east, with most of the localities known from the south Mediterranean region (Assmann et al., 2018;Jaskuła, 2015;Lisa, 2002;Matalin & Chikatunov, 2016;Putchkov & Matalin, 2003;Serrano, 2013;Wiesner, 2020). In Maghreb, the species is widespread and recognized as euryoecious, inhabiting the highest number of habitats among all known Cicindelidae species recorded from this area (Jaskuła, 2015;Jaskuła & Płóciennik, 2020).
Moreover, it can be characterized both as species with the widest altitudinal distribution and the longest phenological activity among all tiger beetles known from this region .
Based on the wide distribution of Lophyra flexuosa and its large habitat spectrum, we hypothesized that the species should possibly show morphological variability observed not only in the sexual dimorphism in body size (which is regularly observed in tiger beetles) but also in the geographic variability (particular populations are often divided by geographic barriers, especially in mountain massifs and desert areas), which is commonly found in taxa characterized by large geographic ranges. Therefore, the aim of the following research was to test the following hypotheses: total body length, some of the morphological parameters (e.g., mandibles because of their function in males during courtship) show higher values (i.e., are relatively bigger) in males than in females.

The average body size (values of the morphological parameters) of
the individuals differs between the study sites located in different geographic regions and bioclimatic ecozones.

| Field sampling
Adult tiger beetles were collected by entomological hand nets dur-

| Statistical analysis
To test the variation of morphometric traits, measurements of eight body parameters ( In order to study sexual dimorphism, we first compared the measured values of the studied body parameters between males and females separately for each country. Next, right mandible length, length of head, width of head, pronotum length, maximum pronotum width, elytra length, and maximum elytra width were standardized on total body length by dividing the measured values by the total body length for each individual. These standardized values were also compared between males and females for both countries separately. In many cases Kolmogorov-Smirnov tests rejected normal distribution of the data. Therefore, the measured and standardized values were tested for statistically significant differences by applying non-  (Clarke & Gorley, 2001).
To check if there is any relation between L. flexuosa body size and altitude, Spearman correlation was done.

| D ISCUSS I ON
As suggested by Losos and Miles (1994), morphology is determined by both genotype and phenotype, so it can provide insights into the phylogeny and ecology of a studied taxon and the selective pressures driving its evolution. Prior to our study, interspecific and intersexual body shape variations were observed only in a single tiger beetle species but not yet quantified for any Lophyra species nor for any North African Cicindelidae. Moreover, this study is the first In the studied populations of Lophyra flexuosa from the Maghreb region, females are bigger and wider than males (Figure 2), both in the case of the entire population and in each investigated country.
This clearly suggests that such sexual dimorphism is characteristic for the entire species and does not depend on geographic region.
Our findings confirm earlier studies on other Cicindelidae species (e.g., Jaskuła, 2005;Pearson & Vogler, 2001), with the exception of species classified in the Manticorini tribe in which males are characterized by bigger body size (Mareš, 2002). Although in tiger beetles differences in body size are also dependent on food availability during the larval stages (Pearson & Knisley, 1985), generally it is known as strongly connected with sex of the beetle and known as sexual dimorphism (Pearson & Vogler, 2001). The bigger body size found in females is usually explained by the role of this sex in mating behavior.
As it was found in many different taxonomical insect groups, females invest much more energy in reproduction process than males, as a result a bigger size is much more beneficial for this sex (Thornhill & Alcock, 1983). First, females have to produce eggs, which need to be supplied in substances used in larval development, and second, they also need to find a good place to deposit them. These are among the most crucial conditions in females' post-copulatory reproductive behavior as they determine developmental success of their embryos and as a consequence have significant impact on overall reproductive success. In contrast, males usually invest only their sperm, as a result their energetic costs during courtship are much smaller. All these elements of mating behavior can be easily found in tiger beetle species (Pearson & Vogler, 2001).
The bigger body size of females is often explained also by male show that bigger females are preferred by males (e.g., Crespi, 1989;Gwynne, 1981;Harari et al., 1999;Johnson, 1992;Sota et al., 2000;Thornhill & Alcock, 1983). Such males' strategy can be easily explained if we note that bigger females can potentially produce and lay a higher number of eggs and/or they can supply the eggs in much more substances for better development of embryos. As a consequence, a male which will copulate with such kind of females may potentially increase his reproductive success (Thornhill & Alcock, 1983).
Although we noted that most of the measured body parameters had higher values in females, we also found that values of some parameters were higher in males of Lophyra flexuosa, especially when standardized on total body length (Figure 2), namely length of pronotum, length of head, and right mandible length. On the other hand, differences in shape, size, and even in colors of mouthparts in tiger beetles were noted earlier in some other Cicindelidae species as an example of significant sexual dimorphism. For example, Kritsky and Simon (1995) found smaller central teeth of mandibles and shorter labrum in some North American taxa. A shorter labrum was recorded also in case of, for example, the African genus Neochila by Cassola and Bouyer (2007), who noted also different coloration of mandibles and labrum between sexes, as well as in South American Oxycheila (Wiesner, 1999) and Pseudochycheila (Cassola, 1998).
Much longer mandibles are characteristic also for males of all known members of the African tribe Manticorini (Mareš, 2002) and were found in a very common central European species Cicindela hybrida (Jaskuła, 2005). All these differences in size and shape of mandibles and labrum between males and females of tiger beetles can be explained by the role of these parts of mouthparts during courtship as smaller teeth of mandibles and shorter labrum allow males to better maintain and grasp the female's thorax during copulation (Pearson & Vogler, 2001). Moreover, as it was suggested in an earlier study (Jaskuła, 2005), longer mandibles and wider distance between their bases means greater length between the end parts of these organs, when mandibles are fully opened, what probably allows catching and grasping bigger females during mating, and as a consequence, help males with longer mandibles to increase their reproductive success.
Mandible length has a special meaning, because, as in case of other Cicindelidae species (e.g., Gilbert, 1997;Rewicz & Jaskuła, 2018), also in L. flexuosa, mandibles are used by both sexes to catch and kill prey, as a consequence their size is sometimes mentioned as a very important factor determining types (and size) of prey during hunting behavior (Pearson & Mury, 1979). Different sizes and shapes of mandibles were also noted between tiger beetle species which co-occur in one type of habitat as a possible way to reduce food competition between such species (e.g., Pearson & Juliano, 1991;Pearson & Mury, 1979;Satoh et al., 2003).
The analysis of body parameters allowed to recognize two morphological groups in Lophyra flexuosa which are separated geographically (Figures 3 and 4). Individuals occurring in eastern Maghreb (Tunisia) were noted as significantly larger in comparison with those from the western region (Morocco). Such a significant difference is rather unexpected as the population from entire North Africa (including both studied countries) is classified as one subspecies-Lophyra flexuosa flexuosa (Putchkov & Matalin, 2003;Wiesner, 2020). Although we had no opportunity to study specimens from Algeria, which is placed in central Maghreb just between Morocco and Tunisia and definitely they would be necessary to provide a full overview for the studied problem, we were able to note that the body size of Lophyra flexuosa shows a negative correlation with altitude, both in the case when the entire population was analyzed and the Moroccan population ( Figure 5). Such results can be compared with some other studies as the body size of many animals, including insects, frequently varies also with altitude (e.g., Blanckenhorn et al., 2006;Partridge & Coyne, 1997;Stillwell et al., 2007). Moreover, as it was shown by Stillwell and Fox (2009) variation in body size, growth, and life-history traits of ectotherms along altitudinal gradients is generally assumed to represent adaptation to local environmental conditions, especially to temperature. However, the degree to which the variation along such clines due to adaptation versus plasticity is still poorly studied and understood. On the other hand, we also found that altitude was not a factor which morphologically separated populations from Tunisia and Morocco. The significant differences observed in body size both in males and females suggest high plasticity of this species and/or a long-term geographic isolation of both populations. This probably can be explained not only by the large geographic distance between them but also by the large number of natural barriers (especially particular mountain ranges of the Atlas Mts. as well as desert areas) (Blondel et al., 2010;Houérou, 2009). As noted above, an opportunity to study additional material Sciences -SGGW.

CO N FLI C T O F I NTE R E S T
All authors declare no conflict of interest including any financial, personal, or other relationships with other people or organizations within 3 years from the beginning of the submitted work that could inappropriately influence, or be perceived to influence, their work.
All authors declare that species studied in the text is not threatened or protected by law in any of the studied countries. Moreover, material was collected outside of any protected area as a result no special permissions were necessary during field work.

DATA AVA I L A B I L I T Y S TAT E M E N T
The file with raw data is available in the Dryad database under the