Neotrop Entomol (2016) 45:33–43 DOI 10.1007/s13744-015-0341-2

ECOLOGY, BEHAVIOR AND BIONOMICS

Population Dynamics of the Swallowtail polystictus polystictus (Butler) (: Papilionidae) with Notes on Its Natural History

1 2 1 1 VW SCALCO ,ABBDE MORAIS ,HPROMANOWSKI ,NOMEGA

1Depto de Zoologia, Univ Federal do Rio Grande do Sul, Porto Alegre, RS, Brasil 2Depto de Biologia, Univ Federal de Santa Maria, Santa Maria, RS, Brasil

Keywords Abstract , ecological transition zone, (Butler) is a butterfly from the Neotropical region, oc- mark-release-recapture, Neotropical region curring in the Atlantic Forest and Pampa biomes. It is commonly found in Correspondence forest fragments surrounded by meadow formations, subjected to marked VW Scalco, Graduate Program in seasonal changes. Here, we report the population dynamics of Biology, Federal Univ of Rio Grande do Sul, Bento Gonçalves Ave. 9500/43435, Postal B. polystictus at a high latitude environment and provide notes on its Code 91501-970 Porto Alegre, RS, Brasil; natural history. Population parameters were estimated on a 12-month [email protected] mark-recapture program and the seasonality of resources investigated Edited André VL Freitas – Unicamp by exhaustive mapping of host-plants and flowers. The number of butter- flies per day was not stable during the year, ranging from zero (winter) to Received 12 February 2015 and accepted 29 22 (summer); the sex ratio was always male biased (3M:1F). The age struc- September 2015 Published online: 20 November 2015 ture was not constant, with an increase of older individuals toward sum- mer. The population density was positively correlated with temperature, * Sociedade Entomológica do Brasil 2015 relative humidity, and day length. The residence time was lower for males, while the vagility was lower for females; the increment of resources at forest edges seems to increase the likelihood of occurrence of both sexes. The results shown here suggest that South Brazilian populations of B. polystictus have high ecological demands for spring and summer condi- tions, avoiding winter in diapause.

Introduction marked seasonal variation regarding temperature of photo- period. Since these abiotic variables are considered two of Population dynamics is a central theme in ecology, unifying the most important factors shaping developmental patterns concepts that permeate this field of science. It is a field of and behavior of swallowtail (Tyler et al 1994, extensive application for understanding pest , epide- Scriber et al 1995,Lehnertet al 2012), the population dynam- miology, biological control, and conservation (Price et al ics at high latitude sites should be better investigated to 2011). In recent years, knowledge on butterfly biology has improve the mechanistic understanding of population pa- increased due to research efforts on natural history and pop- rameters that changes along the Neotropics. ulation dynamics of many different species, and several of The New World genus Battus Scopoli has 12 spe- them in the past three decades have been focused on cies with widespread distribution from Central to Troidini from the Neotropical region (Brown et al 1981, the South United States. One characteristic of this group of Otero & Brown 1986, Freitas & Ramos 2001,Paim&Di butterflies is the exclusive use of host-plants from the genus Mare 2002,Beirãoet al 2012, Herkenhoff et al 2013). Most Aristolochia (Brown et al 1981, Weintraub 1995, Klitzke & of these studies did not find marked fluctuations for the Brown 2000), from which larvae sequester secondary com- analyzed populations, perhaps because most Troidini species pounds during larval development to use as chemical de- were from low latitudes and were not subjected to any fense against predators by improving unpalatability (Nishida 34 Scalco et al.

&Fukami1989,Feeny1995). Some Battus species are sensi- around 24% of the municipality area (Silveira & Miotto 2013). tive to environmental perturbations, requiring habitats with The landscape vegetation consists of a mosaic of formations intermediately to highly preserved conditions, making them typical from the ecological transition zone between the a useful bioindicator to monitor anthropic disturbance (Tyler Atlantic Forest and Pampa biomes, ranging from open grass- et al 1994). Thus, knowing the dynamics and ecological pref- lands in the northern face to semi-deciduous seasonal forest erences of such species is a cost-efficient tool for habitat in the southern face (Fig 1). The area is interconnected with monitoring. some primary forest remnants from other hills and shows an Battus polystictus polystictus (Butler) (hereafter Battus advanced stage of ecological succession (Backes 2000). The polystictus) has its distribution restricted to the Atlantic climatic and edaphic factors have a strong influence on the Rainforest and Pampa biomes, occurring from south and area physiognomy, determining the occurrence of clean and southeast regions of to northeastern and shrub meadows, forest fragments, and swamps. According Argentina (Tyler et al 1994). Adults display large black wings to the Köppen-Geiger classification (Peel et al 2007), the with greenish-yellow blots at the wing margins, showing sex- region climate is humid subtropical (Cfa). The annual average ual dichromatism regarding abdomen coloration. They usu- temperature is 19.5°C and the annual rainfall 1324 mm ally fly high and fast, with short periods of gliding in the (Menegat et al 2006), with hot and dry summers (average woodland edges and moist forests, from spring to autumn temperature—24.9°C, average rainfall—98.5 mm) and cold (Núñez-Bustos 2010), generally near hillsides and slopes and wet winters (average temperature—15.2°C, average (Scalco 2012). The species is essentially nectarivorous and rainfall—131 mm). A climatic diagram for the study area dur- visits a wide variety of flowers (DeVries 1987). ing samplings is presented in Fig 2. The objective of the present study was to describe the population dynamics and some aspects of the natural history Butterfly sampling and parameters analyzed of B. polystictus in a seasonal environment at the southern- most area of Brazil. Our hypothesis is that populations of We used the technique of mark-release-recapture (MRR) to Troidini species from southern Brazil are subjected to differ- monitor the population of B. polystictus over a year, from ent environmental constraints when compared to northern November 2012 to October 2013. Field surveys were con- populations. We expect that population size will vary directly ducted 1–3 times a week, except during the winter when field with the day length and temperature, leading to adult local expeditions were done fortnightly. Butterfly sampling was extinction during later autumn, winter, and early spring. The carried out between 09:00 am and 04:00 pm, always on choice to conduct the present study was also related to the sunny days, with temperatures between 15 and 35°C and selective behavior of B. polystictus, mainly for moist forests mild breeze. The sampling counted 45 field days scoring ap- located near hillsides with a low to medium level of distur- proximately 360 net-hours of sampling effort. Butterflies bance. The contact zone between the Atlantic Forest and captured were marked and recaptured along a 2500-m tran- Pampa provides a heterogeneous landscape without the pre- sect located at the southern face of the Morro do Coco. The dominance of forest or meadows. Adult resources and larval trail used for field surveys crossed different vegetation for- host-plants are expected to vary between meadow and for- mations (Fig 1) and was divided into 50-m sectors to allow est fragments; thus, it is expected that B. polystictus will the identification of capture/recapture point of each butter- occur preferentially in forest habits in the study site. High fly. Butterflies were captured with an net and marked ecological demands are common to all endangered species on the underside of discal cells on both hindwings with a of Troidini, and, despite B. polystictus are not being consid- unique numerical code, and then released. The marks were ered a threatened butterfly, we expect that this species will made using a felt-tipped pen with a non-toxic-permanent-ink be better suited by landscapes richer in resource availability. (Ehrlich & Davidson 1960). For each butterfly, the following aspects were recorded: numerical code, time of capture, sex, age, forewing length, sector of capture, and vegetation type Material and Methods in the sector of capture. Sexing was done through the inspection of genitalia and Study site dorsal abdomen color (males have an evident green- yellowish coloration). The sex ratio was estimated monthly The study was carried out at the locality of Morro do Coco, a by scoring the sexual rate observed in each field survey. 300-ha, 131-m high granitic mount (Knob 1978) located in the The age of individuals was estimated visually by the wing Viamão Municipality, state of Rio Grande do Sul, southern wear conditions of captured butterflies (Ehrlich & Gilbert Brazil (30°15′52″S,51°02′47″W). Situated in the shores of the 1973). We scored three categories according to wing wear Guaíba Lake, the study site belongs to the granite mountain (Freitas 1993): young (intense color, very bright), interme- chain present in the surroundings of State Capital, occupying diate (faded color, less bright), and old (very faded color, Population Biology of Battus polystictus 35

Fig 1 Landscape formations present at Morro do Coco, Viamão, RS, Brazil. Meadow (a), hill slope forest (b), lowland moist forest (c), and Restinga forest (d). some damage to the wing, partially transparent). The age between months using appropriate parametric or non- structure was calculated monthly considering both sexes to- parametric tests. The vegetation formations were catego- gether, by scoring the proportion of each category present in rized in four different types: meadows, hill slope forests, each field survey. Forewing length of captured butterflies was lowland moist forests, and Restinga forests. To analyze the measured with a digital caliper (accuracy 0.01 mm) using wing preference of adults for the four types of vegetation, we insertion on the thorax and the terminal portion of vein R4 as scored butterfly captures in each sector regarding the vege- anatomical landmarks. Data on wing size was analyzed for tation and applied a chi-square test to data. Differences re- normal distribution using the Kolmogorov-Smirnov tests garding male and female preferences were analyzed using and after investigated for sexual dimorphism and variation chi-square test for homogeneity. The movements of individuals were estimated as the max- imum vagility observed for each butterfly from the first to the last capture event (including recaptures made on the same day). To calculate the vagility of butterflies captured, we di- vided the trail used for field surveying into 50-m sectors. The vagility was zero when a butterfly was recaptured at the same sector of the first capture event; the vagility was 50 m when the first and the last captures occurred in adjacent sectors, while the maximum vagility was estimated as the sum of 50- m sectors covered by the same butterfly from the first to the last capture event. The Moses Test of Extreme Reaction was used to verify the vagility differences between sexes. To estimate the population size, we used the MRR data considering the number of individuals captured per day and the records of individuals marked and recaptured (Freitas & Ramos 2001). The MRR data was analyzed separately for each sex through the Lincoln-Petersen method with Bailey’s continuity correction for small samples sizes (Bailey 1952). Fig 2 Climatic diagram from November 2012 to October 2013 at Morro The residence time was calculated as an indirect measure do Coco, Viamão, RS, Brazil (according to Walter 1985). Black, superhumid periods; hatched, humid periods. Polygonal line, of longevity, using the minimum number of days between temperature. the first and last capture (Brussard et al 1974). 36 Scalco et al.

We also evaluated the association of seasonal fluctuations Results in number of butterflies with temperature, rainfall, relative humidity, and day length during the study period. The num- Population dynamics ber of butterflies were obtained from MRR data, tempera- ture, insolation, and rainfall data acquired from Brazilian A total of 190 individuals of B. polystictus were captured and Bank of Meteorological Data for Education and Research of marked during 1 year of sampling. The number of butterflies the National Institute of Meteorology (BDMEP 2014) and day captured per day varied from zero to 19 for males (mean= length data from timeanddate.com (Time and Date AS 2015). 4.24±4.06) and from zero to seven for females (mean=1.29 Each set of data was calculated as monthly mean and then ±1.42). Butterflies were recaptured from one to three times, analyzed with Spearman’s Rank-Order Correlation test. with most of the butterflies captured only once (82.6%). Nearly 8.9% of butterflies were recaptured once, 6.8% twice, and 1.6% three times. The estimated population size did not Resource phenology, natural history, and behavior differ significantly during samplings (note error bars in Fig 3), but the number of butterflies captured was not stable during The phenology of flowers from different plants occur- the year, showing a clear seasonal pattern. The number of ring along the trail used to sample butterflies was re- butterflies exhibited small peaks from October to November, corded to access information about the nectar sources with an evident increase in the number of butterflies after used by adults. At each sampling occasion, the plants December (Fig 3). The number of butterflies over time was in bloom were identified and the availability of flower significantly correlated with month temperature (r=0.876, resources mapped along the trail using the 50-m sec- p<0.001), relative humidity (r=−0.868, p<0.001), and day tors. After the identification of plants, ad libitum ob- length (r=0.925, p<0.001), but not correlated with rainfall servations (Altmann 1974) during field surveys were (r=0.135, p=0.675). Considering both sexes together, the performed to identify which flowers were visited by maximum number of butterflies was observed in the begin- B. polystictus adults. After the identification of flowers ning of summer. Two marked peaks occurred during the used by adults, the hypothesis of heterogeneous distri- hottest season of the year: the first one in December (65 bution of flowers along the sampling trail was analyzed males, 19 females) and the second one in February (29 males, using a Kolmogorov-Smirnov test to compare the ob- 13 females). After the end of February, the number of but- served and the expected homogeneous distributions. terflies decreased toward the beginning of autumn, when no The hypothesis that the presence of nectar sources adult was registered until the beginning of spring. increases the likelihood of finding a butterfly was test- ed by the association of flower records with butterfly Sex ratio captures using the Spearman’s rank-order correlation test. The sex ratio was male biased (140 males and 50 females The presence of Aristolochia species was mapped in were marked—approximately 3M:1F), with males being sig- the study site to provide data on their availability over nificantly more abundant than females in all months of sur- the months and details on their use as host-plants. The veying (Fig 4; χ2=19.93, p<0.01). The greater dominance of hypothesis that heterogeneous distribution of host- males was observed during December, when a sex ratio of plants along sampling trail increases the likelihood of 6M:1F was found. From all butterflies marked, 22% of males finding a butterfly was tested using the same method and 10% of females were recaptured at least once. Males applied to flowers. At each sampling occasion, were recaptured from one to three times and females from Aristolochia branches from ground level up to six me- one to two times. ters high were inspected for the presence of B. polystictus immature forms. Eventual immature forms Age structure from other Troidini species were also recorded, to ac- cess resource partitioning information. The age structure of the population varied significantly dur- In addition to the population sampling, adult foraging be- ing the study period (χ2=42.24, p<0.001) (Fig 5). At the be- havior, male patrolling, and female oviposition activity were ginning of spring, young butterflies accounted for the major- recorded. The observation method used was the Focal- ity of the individuals captured. With the advance of spring, Animal Sampling (Altmann 1974). Behavioral recordings were the population started to age, with the increase of interme- performed at each sampling occasion, when butterflies were diate and old butterflies and subsequent disappearance of observed during flight before being net-captured. Once cho- young individuals from the population. At the end of spring, sen, the focal butterfly was followed for as long as possible young butterflies started to increase in proportion again. and all behavioral occurrences recorded for further analysis. From January to February, the population showed a mature Population Biology of Battus polystictus 37

while the proportion of old butterflies became stable for some weeks. At the end of summer, an expressive decrease in the proportion of young butterflies occurred, followed by a marked increase in the proportion of the old class. Just after the beginning of autumn, the young and intermediate age classes completely disappeared from the population, with on- ly the old class remaining until the end of autumn.

Wing size

Female wing size was significantly greater than that of the males (females, 50.64±2.40 mm; males, 48.08±4.44 mm; t=−3.612, p<0.001—Table 1). The wing size also showed var- iation within each sex, ranging from 45.61 to 54.88 mm in females and from 41.05 to 58.63 mm in males. The largest wing size of females was observed during December 2012, whereas for males it was during November 2012.

Vegetation type preference

Butterflies significantly differ regarding the preference for the four types of vegetation (χ2=195.053, p<0.0001). Nine adult captures were performed in meadows, 41 in hill forests, 128 in lowland forests, and 12 in Restinga forests, indicating a preference for lowland forests. No significant differences re- garding male and females preferences were observed (χ2= 0.098, p=0.992).

Residence time

Fig 3 Number of males (a) and females (b)ofBattus polystictus from November 2012 to October 2013 at Morro do Coco, Viamão, RS, Brazil. The residence time of males ranged from 1 to 20 days and Black circles are the number of individuals present per day; gray from 1 to 10 days for females, with no significant difference diamonds and vertical lines are the estimated number and standard found between the mean residence time of sexes (male me- error based on the Lincoln-Petersen method. dian=6.0 days; female median=8.5 days; U=40, p=0.330). structure, with all classes presented. At this time, young and intermediate age classes reached the proportion of 40% each, Vagility

Most of the individuals marked were recaptured at the same sector of the first capture event. The butterflies recaptured at different sectors of the study area moved from 100 to 2350 m. The vagility was statistically different between sexes (Moses test UFemales=9, p<0.01; UMales=4, p=0.056). On average, females moved less than males (female=670 m; male=1098 m). The maximum dispersal recorded for a male was 2350 m, while for a female the maximum dispersal was 1050 m. The daily vagility of males varied from 250 to 1700 m and from 0 to 350 m for females.

Resource phenology, natural history, and behavior Fig 4 Sex ratio of Battus polystictus from November 2012 to October 2013 at Morro do Coco, Viamão, RS, Brazil. Data presented as the Males and females were active during similar periods of the percentage of males (in black) by month (based on daily means of captures). Data from May 2013 to August 2013 is blank due to the day, searching for nectar in flower buds. The distribution of absence of butterflies during the period. flowers along sampling transect was not homogenous (D= 38 Scalco et al.

open-field areas. Females were seen more frequently flying at lower heights when compared to males. On sunny days, males exhibited intense patrolling and territorial displays. Hill-topping behavior was observed in males during the warmer periods of the day, generally be- tween 12:00 am and 2:00 pm. Males defended territories at the highest point of the forest canopy, exhibiting agonistic behavior toward patrolling males. When a foraging female approached a defended territory, the male descended from the canopy and started courtship behavior by executing many loops around the female. Nevertheless, when the tem- perature became too high, the flying activity of the males Fig 5 Age structure of Battus polystictus population from November 2012 to October 2013 at Morro do Coco, Viamão, RS, Brazil. Black, decreased. Females, which generally fly in shaded areas, young individuals; crosshatched, intermediate; gray, old. The white seemed to be less affected by the temperature rising. area from May 2013 to August 2013 represents the absence of Field surveys showed that two Aristolochia species were butterflies during this period. present at the study site: Aristolochia triangularis and Aristolochia sessilifolia. The former species was available dur- ing all the study period in forest borders, with higher abun- 0.7, p<0.0001). The most abundant nectar resource used by dance during spring and summer. In the winter, B. polystictus butterflies was (Verbenaceae) A. triangularis stops growing, but maintains some green flowers, which were available throughout the year. Battus leaves during the coldest months. On the other hand, polystictus wasalsospottedfeedingonInga uruguensis A. sessilifolia was only available from late spring to early (Fabaceae) and Justicia brasiliana (Acanthaceae) flowers in autumn, being restricted to the open-field areas. This plant December and January. During February and March, the but- scored less than 1% of the total of Aristolochia present at the terflies were seen on Luehea divaricata (Malvaceae) flowers, locality and shows leaf fall during low temperature months while a few butterflies present in April were eventually seen (June to August). Both Aristolochia species had heteroge- visiting Eucalyptus (Myrtaceae) flowers. The presence of neous distribution along sampling transect (U=0.67, those four types of flowers along the trail was strongly cor- p<0.0001), and the presence of these two host-species along related with butterfly records (r=0.917, p<0.001). the trail was not correlated with butterfly records (r=0.035, Males started to patrol in search for females as day tem- p=0.809). perature increased, while females began to search for host- The oviposition behavior of females was observed only in plants to lay eggs. During foraging, B. polystictus butterflies A. triangularis and was generally recorded between 02:00 were sighted flying between 1 and 20 m high, in different and 04:00 pm. The behavioral sequence of oviposition kinds of wooded environments, like closed forests, forest started with leaf selection on a plant, near the ground level, edges, forest canopies, and riparian forests but rarely at with the female flying toward the top of the host-plant, performing several drumming on the surface of leaves with Table 1 Wing size (mm) for females and males of Battus polystictus forelegs without landing. Eggs were laid on stems, stalks, and polystictus from November 2012 to October 2013 at Morro do Coco, on the abaxial surface of young leaves near the apical meri- Viamão, RS, Brazil. stem. Battus polystictus female laid eggs in clusters ranging from 13 to 18 eggs, only above 3 m high. Year Month Wing size (mean±standard error)

Females (n)Males(n) Discussion 2012 November 51.0±0.07 (2) 49.2±1.55 (4) December 52.6±1.32 (8) 48.7±7.37 (50) Population dynamics 2013 January 50.6±1.85 (15) 48.3±2.43 (52) February 50.9±2.25 (16) 46.9±1.91 (17) The demographic patterns observed here for B. polystictus September 47.6±2.30 (4) 47.5±0.18 (2) were similar to those observed for agavus studied at October 48.7±3.26 (5) 45.8±1.63 (12) the same latitude, e.g., the largest population growth oc- Average 50.6±2.40 48.1±4.44 curred in the summer between December and January and the disappearance of adults started in May (Paim & Di Mare The number between parentheses represents the amount of individuals marked during the period. Data from May to August is not shown due to 2002). On the other hand, when compared to the results the absence of butterflies during the period. obtained for Troidini species studied at lower latitudes, the Population Biology of Battus polystictus 39 demographic pattern of B. polystictus differs from those ob- temperature, relative humidity and day lenght could be con- served for several other butterfly species (Cook et al 1971, sidered associated with the disappearance of adults during Brown et al 1981, Tyler et al 1994, Freitas & Ramos 2001, the winter. Yet, the reasons why a tightly synchronized Beirão et al 2012, Herkenhoff et al 2013). Populations of unimodal adult emergence did not occur at the beginning B. polystictus showed two marked peaks, one during late of spring at latitude 30°S for the B. polystictus population, spring and another in late summer, whereas most of the as observed for some Nearctic Region Papilionidae (Emmel & other Troidini species studied for longer periods exhibited Emmel 1969,Sims1980), are not known. no clear population peaks. The only exception was Battus Generally, climatic factors such as temperature and hu- polydamas populations from southeast Brazil, which showed midity are directly related to the abundance of a similar pattern of higher numbers of butterflies during the (Pinheiro et al 2002), and this also seems to be the case of hottest months of the year, followed by a remarkable de- B. polystictus. The major population decline was seen in crease in number toward winter (Brown et al 1981). One March, coincident with the decrease in temperature, as seen possible explanation for this pattern could be the occurrence in other Lepidoptera species at the same latitude (Saalfed & of a similar behavior regarding climate variation present only Araújo 1981, Romanowski et al 1985,Mega2014). in the Battus genus. We recorded an excess of males in the B. polystictus pop- The population of B. polystictus studied showed a pro- ulation during all months of sampling. Several studies done gressive increase of abundance toward late spring and sum- with Papilionidae also recorded the excess of males during mer. Such result suggests a gradual recruitment of individ- field surveys (Brown et al 1995,Paim&DiMare2002,Beirão uals that spent winter as pupae (winter diapause). Unlike the et al 2012, Herkenhoff et al 2013), although Neotropical temperate zone in North America, where the major flight Troidini broods reared under laboratory conditions generally activity of (Linnaeus) occurs primarily in produced a 1:1 proportion between males and females April and is derived from overwintering pupae in diapause (Brown et al 1995). According to Brussard & Ehrlich (1970), (Sims & Shapiro 1983), young B. polystictus butterflies start several reasons may produce the male-biased sex ratios ob- to recolonize the 30°S latitude populations gradually. Some served in mark-release-recapture studies, (i.e., genetic sex studies have shown that termination of diapause occurs with ratio male-biased, differential mortality of larvae or pupae, the increasing of daylight (Wang et al 2009) and tempera- behavioral differences between the sexes) and the precise ture (Scriber et al 2002, Scriber & Sonke 2011) in the spring cause behind such patterns must be addressed under con- and also with the arrival of rain (humidity increasing) (Sims & trolled experimental design. Future controlled experiments Shapiro 1983, Yamamoto et al 2011), but to the present date, should be performed to clarify the reasons why B. polystictus we cannot assure which factors are related to B. polystictus populations show male-biased sex ratios, addressing ques- diapause reversal. tions regarding sex-related behavioral differences, Another difference between the B. polystictus population protandry, and sex proportion modification by the bacterium and other lower latitude Troidini populations was the occur- Wolbachia. rence of local disappearance of adults during the coldest Several studies have shown that the degree of wing scale months of the year. While B. polystictus and P. agavus indi- loss is a sensible predictor of adult age (Young 1971, Ehrlich & viduals from Southern Brazil were not recorded during the Gilbert 1973, Kuefler et al 2008). Thus, long-term monitoring winter (present study; Paim & Di Mare 2002), the Troidini of age structure can be used as a good parameter to deter- butterflies from lower latitudes were observed over the mine the succession dynamics inside butterfly populations. whole year despite the pronounced decrease in population The age structure of the B. polystictus population varied dur- numbers toward the dry season. Since no migratory behavior ing the study period, and the age structuring agreed with the is known for any Troidini species, the results presented here estimates produced by MRR. At the beginning of spring, suggest that the recruitment of individuals from pupae young butterflies accounted for 50% of the captures, sug- ceased with the arrival of autumn. Thus, the population gesting the recruitment of individuals that had spent winter starts an aging process until the last adult dies and the re- in pupae diapause. With the advance of spring, intermediate maining immatures go into pupal diapause, as happens in and old butterflies became more frequent, suggesting an some North American Papilionidae species (Sims 1983,Tyler aging of individuals that had emerged in late September. et al 1994 ). Temperatures can drop from 40°C to 0°C and Such butterflies probably acted as genitors for the subse- relative humidity can increase from 50% to 90% from the quent generation, which started to emerge from pupae at summer to the winter close to Porto Alegre city (BDMEP the end of spring. Such hypothesis is supported by the in- 2014), while the photoperiod decreases from 14 to 10 h of crease of young individuals in December, which once again light per day. Such conditions make butterfly foraging activ- suffered an aging process with the advance of the season. ities incompatible with winter climate conditions. Since rain- From January to February, the population showed a complex fall was not correlated with the number of butterflies, only and mature structure, since young and intermediate 40 Scalco et al. butterflies accounted for approximately 80% of the popula- movements of adult butterflies in a population depends on tion, whereas the proportion of old butterflies became stable the species biology and is deeply related to the availability of near 10%. At the end of summer, an expressive decrease in resources to larvae and adults (Ehrlich & Gilbert 1973), as well the amount of young butterflies occurred, followed by a as to mating strategies (Scott 1972). Also, the flight differ- marked increase in the proportion of old individuals. Once ences between the sexes are found in other species of swal- again, the population diminished the recruitment of hatched lowtail butterflies (Watanabe et al 1985). These butterflies individuals from pupae, but this time the results suggested usually have good flight capacity due to their big thoracic that no further generation would replace the old and dying muscles, allowing them to fly across hostile habitats to genitors from previous generations. At the beginning of au- search for food and oviposition sources (Tyler et al 1994). tumn, with the end of long and hot days of summer, the However, despite having the possibility of dispersal, many young and intermediate individuals completely disappear species show resident behavior as a from the population. Such evidences suggest that the popu- consequence of their habitat fidelity, as recorded for lation decreased in numbers as a response to physiological Parides genus (Otero & Brown 1986,Beirãoet al 2012, modifications occurring in the development of immatures, Herkenhoff et al 2013) and due to territorial behavior, as which started to suffer physiological modifications to over- observed in some Papilio species (Lederhouse 1995, Scott come the short and cold days of the winter as pupae. The 1983). During field survey, some B. polystictus males were recruitment of individuals from pupal diapause only started sighted defending territories near adult food sources at the again in the next spring. These results are also in agreement forest canopy. Similar behavior is observed in B. polydamas, with population size estimates produced by the Lincoln- where 90% of the males tend to be more resident than Petersen method, which indicated a lower population size females as a consequence of mating strategy choice (Young during October. 1971). Despite the similarities between the behavior of these As observed for other butterfly species, females were gen- two Battus species, just a small part of B. polystictus males erally bigger than males. Such pattern is common among observed in field were performing territorial defense, while Lepidoptera, since allometric and life-history theories predict the great majority was sighted doing patrolling behavior. The that the higher abdominal mass of females, which are related short residence time recorded for males when compared to to oviposition behavior, may positively influence the body females reinforces the hypothesis that the territorial behav- size (García-Barros 2000). On the other hand, the ior of males may be an alternative mating strategy, as ob- intrassexual variation in the wing size may be related to the served for many butterflies (Scott 1972,Choe&Crespi1997, nutritional quality of host-plants and to the quantity of food Hernández & Benson 1998). consumed by the immature during development, as well as abiotic conditions influencing larval development (Schappert Natural history, behavior, and the consequences &Shore1998,Rodrigues&Moreira2004,Jorgeet al 2011, for population dynamics Mega 2014). Regarding the residence time, B. polystictus butterflies Several factors can influence the structure of populations, had lower residence than other Troidini species from Brazil and among the most important ones are the distribution (Cook et al 1971, Freitas & Ramos 2001, Paim & Di Mare and the abundance of food resources for adults and imma- 2002,Beirãoet al 2012, Herkenhoff et al 2013), but higher ture stages (Ehrlich 1984, Jansen et al 2012) and also the when compared to North American Papilionidae species mating strategy used by adults. Furthermore, the abundance (Scott 1973,Matsumoto1985). While some Parnassius but- of tropical insects is also influenced by the seasonality of terflies can be resident for approximately 2 weeks in the resource availability (Wolda 1978, Fagua et al 1998, Nylin same natural area, B. polystictus individuals can reside in et al 2005). Concerning the presence of adult resources, the same area for up to 3 weeks and some Parides butterflies the abundance of B. polystictus was related to the availability for about 2 months. These differences probably reflect dis- of flowers, since capture events occurred more frequently tinct habitat selection preferences, since Parides species gen- were near nectar sources. Some flowers present at the study erally choose closed forest environments, Battus species se- site, such as L. camara, were present throughout the year, lect forest borders, and Parnassius species are commonly whereas flowers from other species, such as I. uruguensis, found in open-field areas (Tyler et al 1994). L. divaricata,andJ. brasiliana, bloomed in different months Battus polystictus seems to be much more mobile than of the year. Therefore, the foraging and mating strategies, as the Neotropical Parides species. While some Parides from well as the population dynamics of B. polystictus,seemto Brazil moved about 250 m during their adult stage, reaching reflect in part the environmental heterogeneity of their up to 950 m (Freitas & Ramos 2001,Beirãoet al 2012, home range area. A similar trend was observed for Battus Herkenhoff et al 2013), B. polystictus butterflies moved about devilliersii (Godart) (Ríos & Canamero 2010), a species with 900 m, with a maximum distance of 2350 m. The pattern of similar ecological requirements. Population Biology of Battus polystictus 41

Considering the resources available for immature stages, of high-quality host-plants as a consequence of Aristolochia two host-plant species were found at the study site, vegetative growth. This large offer of host-plants may also A. sessilifolia and A. triangularis, the latter being more abun- produce an increase in the population numbers, producing a dant. Nevertheless, the differences in habitat preferences of modification in the life-histories of competing individuals, these two plant species, the seasonal variation in abundance, reflecting on the decrease of wing size toward late summer. and the foraging characteristics of B. polystictus females sug- To our knowledge, studies of this kind with Troidini species gest that A. sessilifolia is not explored as host-plant at the have not been conducted, and accurate information on the study site. The Troidini female butterflies are very selective phenotypic plasticity in size for this taxon is not known. when choosing a plant for oviposition, seeking for high- Here, we demonstrated that B. polystictus populations quality plants that are suitable as larval food (Tyler et al from higher latitudes are bivoltine and are influenced by 1994,Nishida1995). The interesting thing about seasonal fluctuations regarding temperature variation, unlike B. polystictus oviposition behavior was that female only laid northern populations from other Troidini species. At the in- eggs on A. triangularis branches over 3 m high. Battus terface of the Atlantic Forest and Pampa biomes, polystictus are syntopic with other Troidini species at the B. polystictus is more likely to be found in lowland forests, study site, namely B. polydamas (Linnaeus), exploring resources with heterogeneous distribution along (Drury), Parides anchises (Linnaeus), and Parides bunichus forest edges. Other species seem to share and compete for (Hübner). Those species use the same host-plants the same resources, providing a background condition to the (Beccaloni et al 2008), suggesting the occurrence of resource evolution of alternative foraging and host-plant use strate- partitioning among them. Since the solitary Parides larvae gies. We speculate that with the increase of landscape frag- generally prey on other Troidini eggs and smaller larvae, mentation, butterflies exhibit increased vagility to avoid in- while gregarious species (e.g., some Battus) display no can- tense competitive behavior for food and mates. nibalistic tendencies (Brown et al 1981), the present result Management of forest areas in the interface of the Atlantic suggests the B. polystictus behavior must be related to adap- Forest and Pampa should be considered to maintain the but- tive behavior to evade predation by Parides larvae and to terfly populations at minimum viable sizes in Southern Brazil. avoid competition with B. polydamas at the study site. We suspect that such species were subject to some evolutionary process to allow immature resource sharing over time and Acknowledgments The authors are thankful to Mr. E. Bernardes for space, avoiding direct competition. providing access to the area where the study was performed, to the Another individual trait commonly considered under evo- Chico Mendes Institute for Biodiversity Conservation (ICMBio) for the – lutionary pressure is the body size, since it is a plastic trait in collection license (35153 1), and to the National System of Biodiversity Research/National Network for Research and Conservation of Lepidop- which the genotype is affected by the environmental condi- tera (SiSBiota/RedeLep) for the scholarship provided to VWA (grant tions during development (Kingsolver & Huey 2008). Usually, #563332/2010). The authors also thank A. Caporale, D.S. Martins, a larger size retains the best benefits regarding offspring G.A.G. Souza, G.W.G. Atencio, L.L. Fucilini, L.M. Sant’Ana, L.R.F. Verane, legacy (Stillwell & Davidowitz 2010, Allen et al 2011), but M.O. Teixeira, and V.S. Pedrotti for field assistance. V.W.S. was funded by Coordination for the Improvement of Higher Education Personnel the causes of sexual size dimorphism are not well understood (CAPES), H.P.R. by National Council for Scientific and Technological De- (Hu et al 2010). Size deviation toward larger females is a velopment (CNPq), and N.O.M. by CAPES National Postdoctoral Program common pattern for most species of (Johnson (PNPD/CAPES) (grant #23038.8306/2010-62). This is the contribution & Triplehorn 2004) and for some Papilionidae species as #572 of the Department of Zoology from the Federal University of Rio Grande do Sul. well, like P. anchises (Freitas & Ramos 2001), Pterourus homerus (Fabricius) (Lehnert 2008), Parides burchellanus (Westwood) (Beirão et al 2012), and B. polystictus (present study). 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