Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031

Seasonal patterns in the diversity of Apis and non-Apis in an agro-ecosystem: A case study from eastern dry zone of Karnataka

Arati Pannure* and K. Chandrashekara

Department of Entomology, University of Agricultural Sciences, Gandhi Krishi Vigyan Kendra, Bangalore - 560065, India *E-mail: [email protected]

ABSTRACT

A study has been taken up to investigate seasonal patterns in the diversity of fauna in different landscape elements of GKVK farming system, Bangalore. The study was carried out over a period of one year from August, 2009 to October, 2010. During sampling, a total of 2030 bees were collected which belong to 20 genera and 65 species. In this paper, the temporal variation in abundance of bee species is examined and compared the patterns in different species. The study concluded that there was a trend towards increased bee abundance and richness during winter with increased flowering with a subsequent decline over the course of the summer season. The assessment of diversity of any taxon at a given temporal or spatial scale is important for its conservation and management.

KEY WORDS: Agroecosystem, Apis, Halictids, Megachilids, Non-Apis bees

INTRODUCTION (Heemert et al., 1990; Tuell et al., 2009). Moreover, their populations and Apoidea has an important role as diversity also serve as bioindicators of pollinating agents in the ecosystem. the state of many environments Among the pollinator groups, honey (Tscharntke et al., 1998; Keven, 1999; bees have been considered a priority Steffan-Dewenter et al., 2002; group. In addition to honey bees, non- Tylianakis et al., 2004). They are the Apis bees have been recognized for their best indicators of overall species vigorous and quite rapid pollination in richness in agroecosystems, together many crops. In recent years, the use of with Coleoptera and Heteroptera (Duelli many non-Apis species of bees has and Obrist, 1998). opened a new era in pollination studies

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031

Both, bee abundance and species year), often corresponds with the richness were subject to marked seasonal flowering of their host plants. For this variations in any habitat. Temporally, reason, solitary species can only benefit bee communities can vary widely on an from flowering crops when the bloom annual, seasonal and even diurnal basis. falls into their active period (Westphal et Temporal variation can be the combined al., 2008). According to Wolfe and result of life history traits and Barrett (1988) temporal changes in the environmental factors (Oertli, 2005). pollinator (bee) fauna occurs over a time These Apiformes as a whole tend to be and highest densities correspond to the mostly diurnal, with daily activities peak flowering seasons. Oertli et al., greatly influenced by such factors as 2005 have shown that changes in the temperature, illumination thresholds, season have a marked effect on the wind and precipitation (Cane et al., ecological patterns shown by a bee 2006). Several studies examined the assemblage. Differences among species community structure of bee populations in the pattern of temporal variation in living on one site but only few studies abundance could have important have attempted to show the bee implications for comparisons of the population fluctuation across seasons diversity and faunal composition of and the years (Oertli et al., 2005). These species assemblages between natural and seasonal variations in bee population are agro-ecosystem in different seasons. The attributed mainly to host plant information about the status of non-Apis phenology. bee population fluctuation, the impact of the changes in farming practice and Plant Phenology and Seasonality agricultural management on the bee in Bees: Bee species have distinct species richness and abundance is very phenologies (Wcislo and Cane, 1996). scanty. In light of these challenges an Bee abundance positively relates to the attempt has been made to study the number of flowering plant species seasonal dynamics of Apis and non-Apis (Williams et al., 2001; Kleijn and bees. Langevelde, 2006; Kearns and Oliveras, 2009). Solitary bees have shorter life MATERIALS AND METHODS cycles than social bee species. Several studies have shown that a limited period The present study was aimed to of activity of many species of solitary understand seasonal patterns of Apis and bees (one or two months during the non- Apis bee fauna of agroecosystems

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031 in GKVK campus, Bangalore. The study traps for three days each month. Bees was carried out over a period of one year were collected with sweep nets only if from August, 2009 to October, 2010. warm temperatures and bright sunshine The campus is located at 12°58’ latitude persist. Bees were collected by direct North and 77°35’ longitude East at an netting on flowering plants between 10- altitude of 930 meters above sea level. 12 am on the same day of the ‘Bee pan All the laboratory work was carried out traps’ collection. Bee pan traps were set in Department of Entomology, out in the field for three days during last University of Agricultural Sciences, week of each month. To evaluate GKVK campus, Bangalore, Karnataka, differences and changes in bee diversity India. throughout the sampling period at GKVK, the occurrence and abundance Climate: GKVK campus comes under of number of individuals of bee genera the Eastern dry zone of Karnataka. It has and species were catalogued for each three seasons. Summers characterized by month. warm, sunny dry weather that occurs from March to June, whereas winters are RESULTS AND DISCUSSION cool and dry from November to The study investigated the February. The rainfall in GKVK is seasonal patterns of the ecologically bimodal with an average precipitation of important bee pollinators in agro- 80 cm. The highest amount of rainfall is ecosystem at GKVK campus using received between July-August monthly surveys. In total, 2030 bees (monsoon), the second rainy season representing 65 species belonging to occurs in September-October (post- three bee families (, Halictidae monsoon) although some amount of and Megachilidae) were recorded. rains also received during summer (Pre- monsoon). Sweep net sampling Sampling Methods: For assessing seasonal patterns, bee fauna was Sweep-net method is sampled using sweep nets and ‘Bee pan indispensable sampling method for traps.’ The collection was made year surveying bee community as it has around from August, 2009 to July, 2010 number of advantages. The monthly with sweep-net and from November, changes in the occurrence pattern were 2009 to October, 2010 using bee pan determined based on the net collection and visual observation. A total of 336

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031 individual bees representing three Ceratina binghami Cockerell, Apis families, 19 genera and 48 species were cerana F., Apis florae F. and Apis collected by sweep-netting. Sweep-net dorsata F. were more common and collections were made exhaustively on abundant in all the sampling months. the flowering plants during August, The species, Nomia westwoodi Gribodo, September, November and December Nomia iridescens Smith, Megachile months. During the later months, only lanata F. , Megachile anthracina Smith, ‘new’ entries of bees were collected in Xylocopa latipes (Drury), Xylocopa sweeps and other common genera and aestuans L., Xylocopa sp. 3, Ceratina species collected earlier were identified hieroglyphica Smith, Ceratina in the field to species and released back. smaragdula (F.), bicincta, The purpose was to collect only Amegilla violacea (Lepeletier), Thyreus representative samples, of the bee fauna sp. 1, Thyreus sp. 2, Thyreus sp. 3 were of GKVK, Bangalore. For further encountered throughout the study period. analysis, the sweep net sampling data was used by scoring for ‘presence’ and The bee species, Steganomus sp., ‘absence’ of each species during the Liptriches sp. 1, Sphecodes sp., sampling bout. Lassioglossum sp. 8, Lithurgus sp., Anthidiellum sp., Megachile hera The monthly collection of bees Bingham, Megachile sp. 3, Coelioxys indicated a variation in their occurrence capitata Smith, Coelioxys confusa, over the study period from August, 2009 Coelioxys basalis Smith, Braunsapis sp., to July, 2010. Both abundance and Xylocopa sp. 5, Amegilla sp were least species richness of bees was observed to common and encountered only during vary across calendar months. In general, one, two or three months. The species, bees were found to be abundant during Nomioides sp., Lassioglossum sp. 3, August, September, October, November, Lassioglossum sp. 4, Euaspis edentata, December, January and February Megachile disjuncta, Megachile sp. 1, (monsoon and winter months) of 2009 Megachile sp. 2, Xylocopa sp. 1, and 2010 and less abundant during Xylocopa sp. 2, Xylocopa sp. 4, March, April, May June and July in Xylocopa sp. 5 occurred in winter 2010. Seasonal occurrence and their months and decreased later in summer. abundance of all bee species caught in The megachilids were active from Sweep-nets are mentioned in the Table September, 2009 to January, 2010 and 1. The species, Halictus sp. 1, Amegilla their numbers decreased drastically in confusa (Smith), Amegilla zonata (L.), summer months.

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031

Net collections yielded a richer biasing the collection towards large, bee fauna in the late rainy and winter active or visually attractive bees and also months when many of the plant were at controlled for variation in sampling peak flowering stage and less in the late effort and time. Bees collected in ‘bee summer when flowering of the many pan traps’ belonged to the families plants in the campus ceased. However, Halictidae, Megachilidae and Apidae, as many polylectic bee species were found was the case with bees collected by throughout the study period. Honeybees sweep-net sampling on flowers and were most abundant throughout the vegetation. Interestingly, however, the study period along with Amegilla, generic and species composition was Xylocopa and Ceratina found in all the very different from that of the sweep- seasons. net. Over all the sampling months the “bee pan traps” yielded 1694 bees Bee pan trap sampling representing three families, 13 genera and 33 species. ‘Bee pan traps’ served the purpose of sampling for bees without

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031

Table 1: Seasonal occurrence and abundance of bee species sampled through Sweep-nets. Based on the observation from August (2009) to July (2010) at GKVK campus. Absent (-), Present (*), Moderately abundant (**) and Abundant (***) Family: Apidae Species Aug Sep Oct Nov Dec Jan Feb March Apr May June July Apis florea *** *** *** *** *** *** *** *** *** *** *** *** Apis cerana *** *** *** *** *** *** *** *** *** *** *** *** Apis dorsata *** *** *** *** *** *** *** *** *** *** *** *** Trigona sp. *** *** *** *** *** *** *** *** *** *** *** *** Ceratina binghami *** *** *** *** *** *** *** ** ** ** ** ** Ceratina hieroglyphica ** ** ** ** ** ** ** * * * * * Ceratina smaragdula * * * * * * * * * * * * Amegilla confusa ** ** ** ** ** ** ** ** ** ** ** * Amegilla zonata ** ** ** ** ** ** ** ** ** ** ** ** Amegilla violacea - - ** ** ** ** ** ** ** * * * Amegilla bicincta - - - ** ** ** ** ** * * * * Amegilla sp. ------* - - - Xylocopa sp. 3 ** ** ** ** ** ** ** ** ** ** ** ** Xylocopa latipes ? * ** ** ** ** * * * * * * Xylocopa aestuans ? * * * * * * * * * * * Xylocopa ruficornis ? ? ? * * * * * * * * * Xylocopa sp. 2 ? ? ? * * * * * * * * * Xylocopa sp. 1 ? ? ? * * * * * * * ? ? Xylocopa sp. 4 ? ? ? * * * * * * * ? ? Xylocopa sp. 5 ------* - - - - - Xylocopa rufescens ------* - - * Braunsapis sp. ------* - -

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Family: Megachilidae

Species Aug Sep Oct Nov Dec Jan Feb March Apr May June July Megachile lanata * * ** *** *** *** ** ** * * * * Megachile anthracina ? * * * * * * * * * * * Euaspis edentata ? * * * * - - - - - * - Megachile disjuncta - - ** ** * * * - - - - - Megachile sp. 1 - - ** ** * * * - - - - - Megachile sp. 2 - - * * * * * - - - - - Megachile sp. 3 - - - * ------Coelioxys confusa - - * * * ------Coelioxys capitata - - * * * ------Coelioxys basalis - - * * * ------Megachile sp. 3 - - - * ------Megachile hera ------* * - - Anthidiellum sp? ------* - - - Lithurgus sp. ------* - - -

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Family: Halictidae

Species Aug Sep Oct Nov Dec Jan Feb March Apr May June July Halictus sp. 1 *** *** *** *** *** *** *** ** ** ** ** ** Nomia irridescens ** ** ** ** ** ** ** ** ** ** ** ** Nomia westwoodi ** ** ** ** ** ** ** ** ** ** ** ** Nomioides sp. * * * * * * * * * * * * Lassioglossum sp. 3 ? ? ? * * * * * * * * * Lassioglossum sp. 4 ** ** ** ** ** ** ** ** * * * * Lassioglossum sp. 8 - - * * ------Steganomus sp. * ------* * * Sphecodes sp. - - * ------Lipotriches sp. 1 ------* - - -

Question mark against Megachile anthracina, Lassioglossum sp. 3, Xylocopa sp. and Euaspis edentata from August to October indicates doubtful identification and hence their activity during these months could not be conclusively ascertained.

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Temporal turnover of the genera and species), December (14 species) and April species in the bee pan traps (14 species). Least numbers of species were The bees (mainly oligolectic) tend to encountered in the month of March followed be seasonally restricted and coincide with by August. The similar pattern was observed the flowering of the host plant. The total for the genera also, with the highest number number of genera and individuals collected being encountered during February (10 in bee pan traps during each sampling month genera) followed by the November and June were counted to assess seasonal changes in (9 genera each). However, there was no diversity and abundance. Most species were apparent variation in the generic collected during the months of November composition between the sampling months (20 species) followed by January (16 (Fig. 1). species), February (16 species) and June (15

Fig. 1. Monthly changes in generic and species composition of bees in Bee pan traps during the successive sampling months from November (2009) to October (2010). Pooled data from three consecutive days (3hours/day) of sampling during each sampling month. followed by February which accounted for Halictidae was more abundant and 274 individuals accounting for 19.00 per dominant than others in all the seasons cent of the total catches. In general, the bee followed by Apidae and the family catches with respect to genera, species and Megachilidae was caught with a very less individuals peaked during the first four frequency. The highest abundance or the months of sampling from November (2009) number of individual bees captured in bee to February (2010) i. e., during winter and pan traps was in January, with 383 bees decreased during the summer months. being captured, and accounting for 25.90 per cent of the total individuals. This was

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031

Monthly changes in the abundance of the Similar to sweep-net method, the bee six most dominant species species diversity in ‘bee pan traps’ also There was remarkable monthly peaked during November followed by variation in abundance of the six most December, January, February. The species diversity was high during winter when dominant species of bees captured in the o ‘bee pan traps’. Halictidae and Apidae were temperatures was fairly low (21 C) which more abundant and dominant than others in also coincided with peak blooming season of bee pan traps and the species richness was the many flowering plants. But, in general noticed to vary between months as bees are known to be active during the mentioned earlier. In addition, some bee warmer months. The variations in the species appeared to have very restricted occurrence of the species during different flight activity period and these were trapped seasons may be due to the activity spans of in bee pan traps only in one or two months. the species mainly solitary bees. The lower numbers of species were found during the The monthly variation in the summer months was possibly due to high abundance bee species for the six most temperature (27o C) which may have common and abundant species of bee in bee resulted in the bees being active outside the pan traps was plotted against time to discern sampling period, i.e., early morning and late seasonal changes (Fig 2). Different species afternoon. In fact ‘bee bowl’ captures are of Halictids peaked during different months. known to be strongly influenced by the Among species belonging to the genus activity level of bees at different times of the Lassioglossum, Lassioglossum sp 2 was day. abundant during November (2009). Lassioglossum sp. 3 and Lassioglossum sp. CONCLUSION 4 exhibited a similar pattern and peaked Bee diversity in the GKVK campus was during January. Halictus sp. 1 was most more in the late rainy and winter months when abundant in January and February (2010), many of the plants were at peak flowering stage while Halictus sp. 3 was abundant during and less in the late summer when flowering of February and March (2010). Ceratina the many plants in the campus ceased. There appeared to be a strong association between binghami which was the only abundant seasonal turnover in the composition of the bee species in the genus Ceratina showed a community and that of the flowering quite a different pattern of activity with a community. Apis sp. and Halictids were most peak in January, and was most active in the abundant and dominant in all the seasons winter months and decreased during the whereas most of the Megachilids were summer months. Among the Apis species seasonally bound and were found active during only Apis florea was present in the in ‘bee October to January months. In contrast, by June pan traps’. The results suggest that in again the generic and species count increased general the most dominant species were all may be because of the planting of many active during post rainy and winter months. flowering plants in campus, and such habitats can continue to provide floral resources. In

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Current Biotica 6(4): 432-444, 2013 ISSN 0973-4031 conclusion, the study clearly indicates that bees time of sampling to effectively capture the daily require microhabitats with diversity of flowering variations in the activity of bees. All these plants and availability of nesting sites. While findings underline the importance of season-long more detailed studies need to be taken up the and year around sampling.

Fig. 2. Seasonal patterns in the abundance of dominant bee species catches in ‘bee pan traps’ at GKVK campus from November (2009) to October (2010).

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[MS received 8 January 2013; MS accepted 24 February 2013]

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