The Occurrence of Junonia evarete (Lepidoptera: Nymphalidae) and Acromyrmex striatus (Hymenoptera: Formicidae) on Paepalanthus polyanthus (Eriocaulaceae)

6 Pages·1995·3.2 MB·

by  Tania Tarabini Castellani

NOTES AND COMMENTS
J. New York Entomol. Soc. 103(3):329-334, 1995
THE OCCURRENCE OF JUNONIA EVARETE
(LEPIDOPTERA: NYMPHALIDAE) AND
ACROMYRMEX STRIATUS (HYMENOPTERA: FORMICIDAE)
ON PAEPALANTHUS POLYANTHUS (ERIOCAULACEAE)
As part of a larger investigation comprising the population dynamics of Paepa-
lanthus polyanthus (Bong.) Kunth (Eriocaulaceae), two main herbivores were re-
corded: Junonia evarete (Lepidoptera: Nymphalidae) and Acromyrmex striatus (Hy-
menoptera: Formicidae).
This study was developed on sand dune slack at Joaquina Beach, Florianopolis,
Santa Catarina State, Brazil (27°36'S; 48°27'W), where 9186 individuals of P. pol-
yanthus were followed and recorded in 3 permanent plots of5 X 5 m, from Decem-
ber, 1986 to December, 1991. During that period the maximum monthly means of
temperature ranged between 24°C and 26°C throughout summer months (December
to March), while the minimal monthly means ranged from 14°C to 17°C in June and
July. The highest pluvial levels were recorded during summerand spring, with hydric
deficits occurring in 1988 (the most severe one), 1989, and 1991, particularly at the
end of autumn and beginning of winter. Paepalanthus polyanthus is a monorcarpic
species, dying after reproduction. Reproduction can occur from the second year of
life on, though, generally, it occurs later (Castellan! et al., in preparation). The flow-
ering begins inJuly with peak in Novemberand fructification occurs from September
to January (d’F9a Neves and Castellani, 1994). In these sites, this population ex-
perienced a density reduction from December, 1986 to May, 1989 due to post-re-
productive mortality ofa great proportion ofplants and low recruitment ofseedlings.
Such recruitment occurred expressively only in June, 1989 and April, 1990 (Fig. 1),
favored by periods of high pluviosity during summer and the beginning of autumn
(Castellani et al., in preparation).
Damage caused by J. evarete occurred from December, 1986 to June, 1989, a
period during which the population of P. polyanthus was predominantly constituted
by established plants of large and intermediate sizes of rosettes (Fig. 1).
Two basic patterns of herbivory were distinguished: caterpillars up to 2 cm make
scrapings that cause lesions to the superficial layer ofthe leaf, while caterpillars over
2 cm are chewers. The caterpillars attack tender leaves specially the intermediate
and the central apical ones. Herbivory does not injure the apical meristematic por-
tion. The plants usually survive and produce new leaves in their normal pattern of
growth.
In the surveys, the highest percentages of plants damaged by caterpillars of J.
evarete occurred during autumn, in March and June, 1987, May, 1988, and April/
May, 1989 (Fig. 1). From September to December, 1987 and 1988, months of re-
production of the host plant, the percentage of vegetative plants exhibiting lesions
330 JOURNAL OF THE NEW YORK ENTOMOLOGICAL SOCIETY Vol. 103(3)
FREQUENCY
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<n 10
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0 50 0 50 0 50 0 50 0 50 0 50 0 50 0 50 0 50^ 0 50 0^ 50^ O 50 0^ 50 ^
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Fig. 1. Percentage ofplants ofPaepalanthuspolyanthusdamagedbyJunoniaevarete(open
areas) and by Acromyrmex striatus (shaded areas) from December 1986 to May 1989 (A) and
from June 1989 to December 1991 (B). The number of vegetative plants alive in the 3 per-
manent plots of25 m^ are indicated above the bars and their size distribution along these years
are represented in the figure below. The size class is based on the diameter of foliar rosette
and is; 1 (0-2.9 cm), 2 (3.0-5.9 cm) ... 13 (36.0-38.9 cm).
caused by J. evarete was low (Fig. 1). These caterpillars are not found on repro-
ductive plants which show a dry foliar rosette. We suggest that the utilization of
leaves of P. polyanthus by J. evarete matches the period during which the plant
population offers large amounts of tender leaves. The absence of herbivory by J.
evarete during the period when the population of P. polyanthus was predominantly
constituted by young individuals (from June, 1989 to December, 1991) might be
related to the small size of these host plants at such sites. Crawley (1983) refers to
1995 NOTES AND COMMENTS 331
the small size of plants as one of the factors that a plant may be unusable by its
herbivores.
According to Otero (1986) and Brown-Jr. (1992), J. evarete occurs in sunny open
areas and their larvae can feed on leaves of Stachytarpheta sp. (Verbenaceae), La-
guncularia sp. (Combretaceae) and many ruderal plants. In the dunes system studied,
Junonia evarete seems to be a herbivorous specialist on Paepalanthus polyanthus.
In the area under observation another 60 species ofplants were recorded throughout
the years, being that none of those plants were utilized by caterpillars ofJ. evarete
(see Castellan! et al., 1995 for details of list of species). In those dunes, there was
no recording of Combretaceae species, and among Verbenaceae there was the oc-
currence of Lantana camara and Vitex megapotamica, on which such species of
Nymphalidae were never observed. Ackery (1984) does not mention Eriocaulaceae
among the host plants for caterpillars of Nymphalidae. So this might be the first
record of herbivory ofJ. evarete - a polyphagous species - for this plant family.
The role of the herbivory by J. evarete as a factor of mortality for P. polyanthus
plants did not seem significant in 1987 and 1988. During these two years the majority
of the plants was affected to a maximum of 5% of its foliar basal area (Table 1).
The rate of herbivory was estimated visually, and the percentage of damaged green
foliar area was quantified. In 1987 all damaged plants that died were small (size
classes from 1 to 4), being that 8 of these presented foliar lesions under or equal to
20%. Such mortalities might not be due to herbivory but be just the mirroring of
the higher risks presented by small sized individuals (Castellani, 1990).
In 1988 no damaged plant died. As in 1987, plants which suffered 60% to 80%
of herbivory reestablished part of their foliage or underwent reproduction.
In 1989 larger lesions of herbivory were observed, along with an increase in the
proportion of plants which died without reproduction.
Dirzo (1985) revises experiments of stripping ofleaves in which only those plants
submitted to maximum rates of foliar loss (100%) tend to die. However, the re-
sponses to herbivory tend to differ from each other due to density, to the abiotic
conditions of plant development (e.g., luminosity and hydric availability) as well as
to the age ofplants (Crawley, 1983, 1988; Dirzo, 1985). Stephens (1971 apud Begon
et al., 1986) argues that repetitive foliar damages in subsequent periods might have
more drastic consequences than just a high damage rate ofjust one episode of her-
bivory.
In 1989, in addition to the fact that the herbivory rate of J. evarete was more
marked, several individuals were damaged in the following years. The higher level
ofdamage in 1989 could be related to the drought stress experiencied in 1988 (win-
ter/spring), once stressed plants could be more herbivored in function of increased
availability of amino-acids or a low ability on the part of stressed individual plants
to defend themselves (Crawley, 1988). However, that doesn’t explain if herbivory is
the main or the only cause of such deaths. Other factors as the proper hydric short-
age, the greater microclimatic rigor, and the aging of those individuals might also
be acting upon mortality (Castellani et al., in preparation).
The main agent responsible for foliar lesions on young plants of P. polyanthus
was the leaf-cutter ant Acromyrmex striatus. The highest percentage ofplants show-
ing damage caused by this ant was recorded in October, 1989. During that month
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332 JOURNAL OF THE NEW YORK ENTOMOLOGICAL SOCIETY Vol. 103(3)
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1995 NOTES AND COMMENTS 333
these ants were observed forming large tracks of foraging in one of the permanent
plots which, on that date, presented the highest density ofseedlings ofP. polyanthus.
Fowler et al. (1986) made a distinction between leaf-cutter ants of forest habitats
and those of open habitats in relation to the kind of vegetation used as a substratum
for the fungus on which they feed. The leaf-cutter ants of forest environments use
almost exclusively the dicotyledons, while the ones of open environments use dicot-
yledons, grasses or both. These authors refer to the A. striatus using grasses, an ob-
servation which seems to agree with the herbivory in young individuals of P. poly-
anthus, a monocotyledon which forms rosettes with linear-lanceolated leaves. How-
ever, A. striatus was seen using leaves and/or flowers ofAndropogon selloanus (Gra-
mineae), Centella asiatica (Umbelliferae), Stylosanthes viscosa (Leguminosae), and
Tibouchina urvilleana (Melastomataceae), which occur neighbouring P. polyanthus in
the sand dune slacks. The relation of this species of leaf-cutter ant to P. polyanthus
seems to have an opportunistic character, and its absence preceding—June, 1989 might
be related to the presence of caterpillars and feces of J. evarete. Tania Tarabini
Castellani, Karla Zanenga Scherer, Lucir Maria Locatelli, Benedito Cortes Lopes,
Departamento de Biologia, Centro de Ciencias Biologicas, Universidade Federal de
Santa Catarina, C.P. 476, Florianopolis, Santa Catarina, Brazil, CEP 88010-970.
LITERATURE CITED
Ackery, P. R. 1984. Systematic and faunistic studies on butterflies. Pages 9-21 in: R. I. Vane-
Wright and P. R. Ackery (eds.). The Biology of Butterflies. Academic Press, London.
Begon, M., J. L. Harper and C. R. Townsend. 1986. Ecology; Individuals, Population and
Communities. Blackwell Scientific Publications, Oxford. 876 pp.
Brown-Jr., K. S. 1992. Borboletas da Serra do Japi: diversidade, habitats, recursosalimentares
e varia^ao temporal. Pages 142-186 in: L. P. C. Morellato (Org.), Historia Natural da
Serra do Japi: Ecologia e Preserva9ao de uma Area Florestal no Sudeste do Brasil.
Editora da UNICAMP & FAPESP, Campinas.
Castellani, T. T. 1990. Aspectos da ecologia reprodutiva de Paepalanthuspolyanthus (Bong.)
Kunth (Eriocaulaceae) nas dunas da Joaquina, Ilha de Santa Catarina, SC. Pages 488-
498 in: ACIESP (ed.), II Simposio de Ecossistemas da Costa Sul e Sudeste Brasileira:
Estrutura, Fun^ao e Manejo. Editora da ACIESP, Sao Paulo.
Castellani, T. T, R. Folchini and K. Z. Scherer. 1995. Varia^ao temporal da vegeta9ao em um
trecho de baixada umida entre dunas, Praia da Joaquina, Florianopolis, SC. Insula 24 (in
press).
Crawley, M. J. 1983. Herbivory: The Dynamics of Animal-Plants Interactions. Blackwell
Scientific Publications, Berkeley. 437 pp.
Crawley, M. J. 1988. Herbivores and plant population dynamics. Pages 367-392 in: A. J.
Davy, M. J. Hutchings and A. R. Watkinson (eds.), Plant Population Ecology. Blackwell
Scientific Publications, Oxford.
d’E9a Neves, F. F. and T. T. Castellani. 1994. Fenologia e aspectos reprodutivos de Paepalan-
thuspolyanthus (Bong.) Kunth (Eri—ocaulaceae) em baixada umida entre dunas na praia
da Joaquina, Ilha de Santa Catarina SC. Insula 23 (in press).
Dirzo, R. 1985. The role ofthe grazing animal. Pages 343-355 in: J. White (ed.). Studies on
Plant Demography; A Festschrift for John L. Harper. Academic Press, London.
Fowler, H. G., L. C. Forti, V. Pereira-da-Silva and N. B. Saes. 1986. Economics of grass-
cutting ants. Pages 18-35 in: C. S. Lofgren and R. K. Vander Meer (eds.). Fire Ants
and Leaf-cutting Ants: Biology and Management. Westview Press, Boulder.
334 JOURNAL OF THE NEW YORK ENTOMOLOGICAL SOCIETY Vol. 103(3)
Otero, L. S. 1986. Borboletas: Livro do Naturalista. Eunda^ao de Assistencia ao Estudante
(MEC-EAE), Rio de Janeiro. 112 pp.
Received 17 May 1995; accepted 4 October 1995.
J. New York Entomol. Soc. 103(3):334-336, 1995
THREE RARE GOMPHIDS FROM THE LOWER
CONNECTICUT RIVER
Three gomphids new to the Connecticut state fauna (Carman 1927) were discov-
ered on sandy beaches of the Connecticut River in Middlesex County, Connecticut:
Gornphus fratenius (Say), Stylurus amnicola (Walsh), and Stylurus spiniceps
(Walsh). All three are rare in New England and there is but little known about the
biology of the two Stylurus species (Carman, 1927; Howe, 1918; Walker, 1958).
Sandy beaches at Cromwell and Portland were visted three to four times a week
m
from 5 June until through 18 August, 1995; on average a 200 to 300 stretch of
beach was walked continuously for a period of five hours during a visit. At both
sites the river is broad (ca. 500 m) and without riffles. The beaches, though more
than 25 miles from the ocean, are tidal with daily water levels often fluctuating as
much as 1 m. Small waves continually influence the shoreline. Sands are fine and
compacted, grading to mud and clay in places.
Gornphus fraternus was observed on the first visit (5 June); the last individual
noted was a worn female on 24 July. Over the first few weeks 4-12 individuals were
seen per visit. Adults landed on sandy areas along the river, well above the current
water level, but away from the shoreline vegetation.
Eclosing and teneral adults ofStylurus were first found inearly July atthe Portland
site. Both Stylurus species were initially thought to be emerging individuals ofGom-
phus fraternus, so little data was collected until the 19th of July, when we realized
our mistake. The next day we arrived by 0830 hr and walked a 200 m section of
the Portland beach until 1600 hr. Five individuals of Stylurus spiniceps and one of
S. amnicola emerged between 1230 and 1430 hr, roughly corresponding to the period
of low tide on that date. Additional emergence data are given in Table 1. On most
sunny days in July and early August we could count on seeing 4 to 6 individuals
emerging; the most we saw on any day was 10. We observed emergences between
1000 and 1700 hr, with activity peaking during tidal lows that were accompanied by
sun. Exuviae were collected from beaches on 20 July, 1 August and 4 August, 1995,
primarily from the wrack line: these included 32 5. spiniceps and 7 S. amnicola. In
the center of the Portland beach, we found 1 or 2 Stylurus exuviae per liner foot of
shoreline (on 20 July). Where the beach narrowed, exuviae were found among the
roots of shoreline shrubbery.
Eclosing larvae left distinctive zipper-like tracks which extended to or above the
wrack line, although the occasional individual eclosed closer to the water. We found