ChapterPDF Available

Insect Outbreaks Revisited

Authors:
... These unparalleled collections were the result of many years of fieldwork undertaken by John and Heidi Anderson, who focused primarily on alpha taxonomy and paleoecological aspects of the flora (Anderson and Anderson, 1983, 1989, 1993, 2018. These abundant and diverse plant fossils have been reassessed in recent decades, with a focus on the documentation of plant-insect interactions (Labandeira, 2012;Labandeira and Anderson, 2005;Labandeira et al., 2018). Previous work on the Molteno Formation floras touched on the presence of both, linear and blotch mines on various plant-hosts, including Dicroidium, Dejerseya, Heidiphyllum and Sphenobaiera (Scott et al., 2004), although some of the traces described were equivocal. ...
... Linear leaf mines have been reported from two Triassic localities in South America, both on Heidiphyllum leaves from the Ladinian-Carnian Santa María Formation in Brazil (Cenci et al., 2013), and the Upper Triassic Cañadón Largo Formation in Argentinean Patagonia (Adami-Rodrigues et al., 2008, 2012; J. M. Robledo and S. Gnaedinger, pers. comm.). ...
... Voltzialean Heidiphyllum leaves appear to have been particularly prone to endophytic herbivory, as evidenced by the numerous occurrences of leaf mining recognized in H. elongatum Retallack from South Africa, Australia and South America (Rozefelds and Sobbe, 1987;Adami-Rodrigues et al., 2008, 2012Labandeira and Anderson, 2005;Labandeira, 2012;Cenci et al., 2013;Labandeira et al., 2018), and this new addition on H. cacheutense. Nevertheless, all these occurrences (~900, almost all of them registered in the Molteno Flora) are linear mines assigned to DTs 41, 71 and 139 , whereas the material from the Quebrada del Durazno locality is to date, the only record of a blotch mine from this time interval. ...
Article
We describe two ichnotaxa —Cuniculonomus parallelus Givulescu emend. Robledo et al. and Foliomacula diffussus ichnogen. et ichnosp. nov.— of insect leaf mines from the Late Triassic of Mendoza, Argentina. The specimens, from the Potrerillos Formation at the Quebrada del Durazno locality, consist of a linear mine on a Yabeiella leaf, and a blotch mine on a Heidiphyllum leaf. The earliest convincing records of leaf mining are all linear mines, dating back to the middle-late Triassic, with the first blotch mines appearing from the Cretaceous onwards. The discovery presented here therefore represents the earliest record of a blotch mine, and demonstrates that strategies of endophytic herbivory diversified considerably earlier than previously thought. The abundant associated paleoentomological fauna from the locality provides a rare opportunity to consider possible producers of these interactions. A definitive identification of the miners however, remains highly speculative, partly due to the paucity of direct analogues of insect lineages with leaf mining larvae this early in the fossil record. The exceptional abundance and quality of fossil preservation of both plants and associated insects at the Quebrada del Durazno locality also provides an opportunity to re-evaluate plant host diversity and possible adaptations to mitigate insect herbivory. The insect mine on Yabeiella is the first, and to date only, record of this type of interaction on a gnetalean host. We consider the presence of dense pubescence on Yabeiella and its affiliated Fraxinopsis seeds, as a potential passive defense mechanism against insect herbivory rather than as an adaptation to environmental conditions.
... Apparently, no hole feeding is recorded from any Pennsylvanian-age flora. Several hole-feeding DTs occur sporadically throughout the Permian, from floras of Euramerica (Beck and Labandeira, 1998;Labandeira and Allen, 2007;Vasilenko, 2007;Labandeira, 2012), Gondwana (Gallego et al., 2003(Gallego et al., , 2014Prevec et al., 2009;Cariglino and Gutiérrez, 2011;de Souza Pinheiro et al., 2012;Slater et al., 2012;Labandeira and Prevec, 2014), and Cathaysia (Glasspool et al., 2003). Collectively, the range of Permian hole-feeding DTs extends to a variety of sizes, polylobate shapes, slot feeding, and other types of intercostal excisions (DT01, DT02, DT03, DT04, DT05, DT07, DT08, and DT78), representing a significant expansion of feeding styles. ...
... This type of surface abrasion and delamination of tissues by mandibulate mouthparts is next found on Middle and Late Pennsylvanian pinnules of the pteridosperm Macroneuropteris scheuchzeri (DT75, DT97) from several Euramerican localities (Scott and Taylor, 1983;Labandeira, 2013). During the Permian, evidence of surface feeding is rare to absent in virtually all floras examined, but when present, has been found to occur on seed plants such as medullosans, gigantopterids, callipterid peltasperms, and taeniopteroid cycadophytes (Beck and Labandeira, 1998;Vasilenko, 2007;Prevec et al., 2009;Labandeira, 2012;Labandeira and Prevec, 2014;Schachat et al., 2014). The variety of surface-feeding damage increases markedly during the Middle Pennsylvanian and through the early Permian to include approximately ten DTs that collectively indicate an expansion of morphologies, autecologies, and behaviors associated with feeding on epidermal and immediately underlying tissues. ...
Article
Full-text available
The Mitchell Creek Flats locality (MCF) contains a flora from the early Permian (Cisuralian) of north-central Texas that has been qualitatively and quantitatively evaluated for insect herbivory. The level of herbivory is average for a middle Cisuralian flora from this region, although there is a relatively modest number of specimens. Three ecological features of this deposit are noteworthy in the context of the larger plant-insect interaction trends across the region. First is a well-balanced distribution across the MCF flora of the five functional feeding groups (FFGs) of external foliage feeding, piercing and sucking, oviposition, galling, and seed predation. These five FFGs encompass 22 discrete insect-mediated damage types (DTs) that indicate a variety of generalized and specialized herbivory. Second is the elevated incidence and diversity of seven gall DTs, indicating an arid environment. Third is the pattern of opportunistic herbivory on the cycadophyte Taeniopteris spp., the single, overwhelmingly dominant host that represents 47.5% of all foliage, 56.9% of all interactions, and 16 of the 22 DTs. This distribution of insect-mediated damage suggests a diverse community of opportunistic, generalized and specialized insect herbivores, including a guild of xeric-adapted gallers engaged in a variety of feeding styles that overwhelmingly targeted Taeniopteris spp. as a host plant. This characterization is consistent with an opportunistic herbivory strategy and supports Feeny's apparency hypothesis, in which the most conspicuous, accessible plant at a site is disproportionately and most extensively herbivorized.
... This mythic figure of the Apocalypse brings forth the subject of pests and outbreaks in its wake, which also prominently features frogs, gnats, flies, livestock pestilence, and locustsdthe plagues of Egypt from the book of Exodus. In fact, the importance of pests and their outbreaks are notoriously recognized since ancient times and broadly investigated to the present day [1,2]. Maybe because of that, the subject is a source of some misunderstandings and biases. ...
Article
Outbreaks are characterized by a sudden increase in population density of a given species, and are recognized as an important phenomenon in both natural and artificial systems. Climate and anthropogenic stressors are the main abiotic drivers of outbreaks directly affecting arthropod populations, or influencing them indirectly through their heterospecifics and resources (e.g., host plants). Both are dose- or intensity-dependent and mainly sublethal when outbreaks are considered. Thus, sublethal stimulation or hormesis is an important phenomenon to consider. However, its study is restricted to a few (agricultural) settings and neglects key complexities of biological systems, including arthropods as an ecocosm of symbionts, the role of arthropod interactions, and the co-occurrence of multiple stressors. Therefore, more research is required to tackle the complexities of biological systems.
... Insect outbreaks are very well documented in scientific literature (Barbosa et al. 2012) and include several fossil records, especially from the Holocene Epoch, within the last 11,000 years (Labandeira 2012). Insect outbreaks may occur in both natural and anthropogenic environments, where biotic and abiotic conditions favor insect development and reproduction, or in situations where the control of their populations is limited (Barbosa et al. 2012). ...
Article
Full-text available
The first detection of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) in Brazil pointed to a gloomy future for South American agriculture in the 2012/2013 harvest, and insecticide sales increased exponentially during 2013 and 2014. However, after this outbreak, the population of this insect returned to manageable levels. This study documents data on H. armigera moth collection using light traps during the outbreak in two locations: (a) western region of the state of Bahia, including population levels of H. armigera and main noctuid pests during the big outbreak (February and March 2013); (b) Federal District, including monthly data for five growing seasons (July 2012-June 2017). During the outbreak, an average of 527.3 moths were collected per trap (cotton crop, March) in the western region of Bahia each night, while the maximum average in the Federal District was 75.4 moths (January). The number of moths decreased in the following growing seasons, and in October 2016, the maximum number was 2.8 moths per trap. Aspects related to the variations of H. armigera and Helicoverpa zea (Boddie) populations, including the study of phenology and relationship with climatic factors and Oceanic Niño Index, were analyzed and discussed. All aspects are approached to contribute to the management of lepidopteran pests, especially H. armigera, in the productive systems of the Brazilian Cerrado.
... The oldest records of leaf-mines date from late Carboniferous (Labandeira and Beall 1990;Castro 1997) and Lower Permian (Pinheiro et al. 2012;Adami-Rodrigues et al. 2004b). Those records increase throughout the Mesozoic and Cenozoic (Hickey and Hodges 1975;Liebhold et al. 1982;Kuroko 1987;Scott et al. 1992;Labandeira et al. 1994Labandeira et al. , 2007Labandeira 1998aLabandeira , 1998bLabandeira , 2012Banerji 2004;Peñalver and Delclòs 2004;Krassilov 2007;Krassilov and Shuklina 2008;Ding et al. 2014;Donovan et al. 2014;Khan et al. 2014;Gunkel and Wappler 2015;Su et al. 2015;Adroit et al. 2016;Jud and Sohn 2016;Möller et al. 2017). In Argentina, Donovan et al. (2016) found mines on dicot leaves from several formations of Cretaceous/Paleogene age in the Chubut province. ...
Article
Full-text available
The study of plant-insect interactions provides valuable information about the ecology of feeding behavior and the relationships between the host plant and the producer insect. Records of feeding traces are relatively rare for the Miocene of South America. Here, new records of plant-insect interactions on dicot leaves and fern fronds from the middle and late Miocene of Argentina are presented. In total, 1204 dicot and fern impressions were analyzed including 384 from the San Jos´e Formation and 856 from the Palo Pintado Formation. Traces of arthropod herbivory are found on 303 foliar impressions, 288 from the Palo Pintado Formation and just 15 from the San Jos´e Formation. Forty-four percent of all traces were found on Thelypteris interrupta (Willd.) Iwatsuki 1963 (Thelypteridaceae), followed by Cedrela fissiliformis Anz´otegui and Horn 2011 (Meliaceae) (15.1%) and Schinus herbstii Anz´otegui 1998 (Anacardiaceae) (11.3%). Thelypteris interrupta is associated with a low diversity of Damage Types, mainly hole and window feedings, indicating a monospecific relationship with the trace maker. On the other hand, the high abundance and diversity of damage types found on C. fissiliformis and S. herbstii denote that these plants were hosting a more diverse group of arthropods. Likewise, the lower number of traces identified in the San Jos´e Formation corresponds to the xeric conditions established during the middle Miocene in northwestern Argentina. These conditions changed in the late Miocene, at least in some regions, to a humid climate, promoting an increase in phytophagy that is evidenced by the abundance recorded in the Palo Pintado Formation.
Article
The use of the functional feeding group–damage type system for analyzing arthropod and pathogen interactions with plants has transformed our understanding of herbivory in fossil plant assemblages by providing data, analyses, and interpretation of the local, regional, and global patterns of a 420-Myr history. The early fossil record can be used to answer major questions about the oldest evidence for herbivory, the early emergence of herbivore associations on land plants, and later expansion on seed plants. The subsequent effects of the Permian–Triassic ecological crisis on herbivore diversity, the resulting formation of biologically diverse herbivore communities on gymnosperms, and major shifts in herbivory ensuing from initial angiosperm diversification are additional issues that need to be addressed. Studies ofherbivory resulting from more recent transient spikes and longer-term climate trends provide important data that are applied to current global change and include herbivore community responses to latitude, altitude, and habitat. Ongoing paleoecological themes remaining to be addressed include the antiquity of modern interactions, differential herbivory between ferns and angiosperms, and origins of modern tropical forests. The expansion of databases that include a multitude of specimens; improvements in sampling strategies; development of new analytical methods; and, importantly, the ability to address conceptually stimulating ecological and evolutionary questions have provided new impetus in this rapidly advancing field.
Chapter
This chapter focuses on the major types of diversity documented in the insect fossil record. Diversity in the insect fossil record typically is provided either at the locality level, with an enumeration of all resident species (tax‐onomic diversity), or more generally has been counts at the genus or, more commonly, the family level, expressed globally through time (taxic diversity). A wide range of techniques, morphological attributes, and modes of presentation document the morphological disparity of fossil (and modern) insects. The trend of insect diversity during the Paleogene and Neogene periods is best described as a sustained increase to the present day, with a capture rate of 63% of the approximately 980 modern insect families a rate that has not changed appreciably with more recent analyses. The concluding discussion incorporates an understanding of why fossil insect diversity is relevant for the current condition of terrestrial and freshwater ecosystems of the planet.
Article
Full-text available
Plants and insects are constantly interacting in complex ways through forest communities since hundreds of millions of years. Those interactions are often related to variations in the climate. Climate change, due to human activities, may have disturbed these relationships in modern ecosystems. Fossil leaf assemblages are thus good opportunities to survey responses of plant-insect interactions to climate variations over the time. The goal of this study is to discuss the possible causes of the differences of plant-insect interactions' patterns in European paleoforests from the Neogene-Quaternary transition. This was accomplished through three fossil leaf assemblages: Willershausen, Berga (both from the late Neogene of Germany) and Bernasso (from the early Quaternary of France). In Willershausen it has been measured that half of the leaves presented insect interactions, 35% of the fossil leaves were impacted by insects in Bernasso and only 25% in Berga. The largest proportion of these interactions in Bernasso were categorized as specialist (mainly due to galling) while in Willershausen and Berga those ones were significantly more generalist. Contrary to previous studies, this study did not support the hypothesis that the mean annual precipitation and temperature were the main factors that impacted the different plant-insect interactions' patterns. However, for the first time, our results tend to support that the hydric seasonality and the mean temperature of the coolest months could be potential factors influencing fossil plant-insect interactions.
Thesis
"If all mankind were to disappear, the world would regenerate back to the rich state of equilibrium that existed ten thousand years ago. If insects were to vanish, the environment would collapse into chaos." Edward O. Wilson Insects are the most diverse animals on Earth, and neatly associated with plants they represent two of the major groups of organisms both in species diversity and biomass quantity. The majority of their interactions involves insect feeding and insect parasitism (such as galls forming) mostly on leaves. Plant and insect compose one of the main trophic levels in ecosystems over the 325 million years. Today, the continuous and fast rising of temperature mostly due to human activities since the last century is disturbing the balance of ecosystems on Earth. This is named "global change". Consequently, to understand the role of plant and insect interactions, through time but also trophic networks, becomes crucial. It is in this general context that the aim of the thesis pursued. The fossil record is an exceptional opportunity to survey responses of plant-insect interaction to climate variations over long time interval through traces of plants reactions caused by interaction with insects, as Earth has already experienced many climate changes. For the last 3 million years (Ma), oscillations between long cold periods, marked by the rifting of ice cap in Northern Hemisphere, and short warm periods have occurred. Europe ecosystems has been particularly impacted by these climatic variations. Therefore, thesis emphasized an interest on some fossil outcrops in Europe during this period. The famous Lagerstätte of Willershausen (middle Germany) was specifically study. It is an exceptional fossil outcrop that contains around 200 angiosperm species for a total of ca. 8000 collected fossil leaves. These leaves testify a paleoforest developed there around 3 — 2.6 Ma ago in a climate warmer than today (mean temperature ca. +5°CUnder these conditions, many plant species typical of the Mediterranean ecosystems were settled there, such as Montpellier maple (Acer monspessulanum L.) or Olive tree (Olea sp.). For comparison, other paleoforests were studied: Berga (similar in age and geographically close to Willershausen) and Bernasso (younger than Willershausen (2.16 — 1.96 Ma) and located in southern France close to Mediterranean. These forests were compared as many common plant taxa were similar between each other. Furthermore, some species today endemic to the Caucasian region, such as Persian ironwood (Parrotia persica (DC.) C.A.Mey) or Caucasian elm (Zelkova carpinifolia (Pall.) Dippel), were also present in these outcrops. The aim of this study is to determine how far the climate differences could be involved in the changes of plant-insect interactions in European paleoforests of the late Pliocene – early Pleistocene. Results highlighted the impacts of both hydric and temperature seasonality, hitherto underestimated in the fossil record, on the patterns of plant-insect interaction in the European paleoforests. It appeared that ecosystems subject to intense hydric seasonality (i.e. important variations of precipitation during the year) could led to higher specialization of plant-insect interaction inferred by higher rate of observed damages du to ‘specialists insects’. In parallel, the coolest temperature during the year seems to be a major factor in the low diversity of damage in paleoforest, presumably due to lower insect metabolism. Absence of convergent correlations between plant richness and damage richness could suggested that influence of climatic factors override impact of these local biotic factors. In order to understand the whole parameters that could have an impact on plant-insect interactions (such as interspecific competition, soil components, taphonomic biases, etc.), our current knowledges are still insufficient to conclude about the relationships between climate and patterns of plant-insect interactions observed in these European paleoforests. It would be wise to make more investigations on modern forests with the methods as applied in fossil record community structure studies. These investigations could help to understand the factors potentially involved in the establishment of a pattern of plant-insect interactions. It is in this perspective that a part of this study was precisely focused on one plant species (P. persica) currently endemic to the Hyrcanian forest (Iran). This forest is supposed to be an analogue forest of the European paleoforests as those studied in this thesis. For now, observations made in Iran tend to corroborate our interpretation. However, the discovery of a new plant-insect interaction only found on leaves of Parrotia persica from both fossil and current forests suggests that historical factors could also have influenced plant-insect interactions observed in the different forests. Finally, the studies on plant-insect interactions in past and extant ecosystems, combined with the study of climatic changes, should permit us to better characterize the relations between plants and insects in forests through time.
Article
Full-text available
To discern the effect of the end-Permian (P-Tr) ecological crisis on land, interactions between plants and their insect herbivores were examined for four time intervals containing ten major floras from the Dolomites of northeastern Italy during a Permian–Triassic interval. These floras are: (i) the Kungurian Tregiovo Flora; (ii) the Wuchiapingian Bletterbach Flora; (iii) three Anisian floras; and (iv) five Ladinian floras. Derived plant–insect interactional data is based on 4242 plant specimens (1995 Permian, 2247 Triassic) allocated to 86 fossil taxa (32 Permian, 56 Triassic), representing lycophytes, sphenophytes, pteridophytes, pteridosperms, ginkgophytes, cycadophytes and coniferophytes from 37 million-year interval (23 m.yr. Permian, 14 m.yr. Triassic). Major Kungurian herbivorized plants were unaffiliated taxa and pteridosperms; later during the Wuchiapingian cycadophytes were predominantly consumed. For the Anisian, pteridosperms and cycadophytes were preferentially consumed, and subordinately pteridophytes, lycophytes and conifers. Ladinian herbivores overwhelming targeted pteridosperms and subordinately cycadophytes and conifers. Throughout the interval the percentage of insect-damaged leaves in bulk floras, as a proportion of total leaves examined, varied from 3.6% for the Kungurian (N = 464 leaves), 1.95% for the Wuchiapingian (N = 1531), 11.65% for the pooled Anisian (N = 1324), to 10.72% for the pooled Ladinian (N = 923), documenting an overall herbivory rise. The percentage of generalized consumption, equivalent to external foliage feeding, consistently exceeded the level of specialized consumption from internal feeding. Generalized damage ranged from 73.6% (Kungurian) of all feeding damage, to 79% (Wuchiapingian), 65.5% (pooled Anisian) and 73.2% (pooled Ladinian). Generalized-to-specialized ratios show minimal change through the interval, although herbivore component community structure (herbivore species feeding on a single plant-host species) increasingly was partitioned from Wuchiapingian to Ladinian. The Paleozoic plant with the richest herbivore component community, the coniferophyte Pseudovoltzia liebeana, harbored four damage types (DTs), whereas its Triassic parallel, the pteridosperm Scytophyllum bergeri housed 11 DTs, almost four times that of P. liebeana. Although generalized DTs of P. liebeana were similar to S. bergeri, there was expansion of Triassic specialized feeding types, including leaf mining. Permian–Triassic generalized herbivory remained relatively constant, but specialized herbivores more finely partitioned plant-host tissues via new feeding modes, especially in the Anisian. Insect-damaged leaf percentages for Dolomites Kungurian and Wuchiapingian floras were similar to those of lower Permian, north-central Texas, but only one-third that of southeastern Brazil. Global herbivore patterns for Early Triassic plant–insect interactions remain unknown.
Article
Full-text available
Using Doyle (1996) as a starting point, we compiled a morphological cladistic matrix of 54 coded taxa (31 wholly extinct, and 23 at least partly extant) and 102 informative characters in order to explore relationships among gymnosperms in general and pteridosperms in particular. Our core analysis omitted six supplementary fossil taxa and yielded 21 most-parsimonious trees that generated two polytomies in the strict consensus tree, both among pteridosperms; the first affected several hydraspermans, and the second affected the three peltasperm/ corystosperm taxa analyzed. The resulting topology broadly resembled topologies generated during previous morphological cladistic analyses that combined substantial numbers of extant and extinct higher taxa. Each of the five groups that include extant taxa was relatively well resolved as monophyletic and yielded the familiar Anthophyte topology (cycads (Ginkgo (conifers (Gnetales, angiosperms)))), strongly contradicting most recent DNA-based studies that placed Gnetales as sister to, or within, conifers. These five extant groups were embedded in the derived half of a morphologically diverse spectrum of extinct taxa that strongly influenced tree topology and elucidated patterns of acquisition of morphological character-states, demonstrating that pteridosperms and other more derived ‘‘stem-group’’ gymnosperms are critical for understanding seed-plant relationships. Collapses in strict consensus trees usually reflected either combinations of data-poor taxa or ‘‘wildcard’’ taxa that combine character states indicating strongly contradictory placements within the broader topology. Including three pro- gymnosperms in the analysis and identifying the aneurophyte progymnosperm as outgroup proved crucial to topological stability. An alternative progymnosperm rooting allowed angiosperms to diverge below cycads as the basalmost of the extant groups, a morphologically unintuitive position but one that angiosperms have oc- cupied in several recent molecular studies. We therefore believe that such topologies reflect inadequate rooting, which is inevitable in analyses of seed plants that use only extant taxa where the outgroups can only be drawn from ferns and/or lycopsids, groups that are separated from extant seed-plants by a vast phylogenetic disconti- nuity that is bridged only by wholly fossil groups. Given the rooting problem, and the poverty of the hypotheses of relationship that can be addressed using only extant taxa, morphology-based trees should be treated as the initial phylogenetic framework, to subsequently be tested using molecular tools and employing not only molec- ular systematics but also evolutionary-developmental genetics to test ambiguous homologies. Among several possible circumscriptions of pteridosperms, we prefer those that imply paraphyly rather than polyphyly and exclude only one monophyletic group, providing one cogent argument for the inclusion of extant cycads in pteridosperms. Although pteridosperms cannot realistically be delimited as a monophyletic group, they remain a valuable informal category for the plexus of gymnosperms from which arose several more readily defined monophyletic groups of seed-plants. The ideal solution of recognizing several monophyletic groups, each of which combines a ‘‘crown-group’’ with one or more pteridosperms, is not yet feasible, due to uncertainties of relationship and difficulties to satisfactorily delimiting the resulting groups using reliable apomorphies. Explo- ration of the matrix demonstrated that coding all of the organs of a plant (extinct or extant) and dividing significantly polymorphic coded taxa are highly desirable, thereby justifying the substantial investment of time required to reconstruct individual conceptual whole plants from disarticulated fossil organs.
Article
Full-text available
Paleoecological studies enhance our understanding of biotic response to climate change because they consider timescales not accessible through laboratory or ecological studies. From 60 to 51 million years ago (Ma), global temperatures gradually warmed to the greatest sustained highs of the last 65 million years. Superimposed on this gradual warming is a transient spike of high temperature and pCO 2 (partial pressure of carbon dioxide in the atmosphere; the Paleocene-Eocene Thermal Maximum 55.8 Ma) and a subsequent short-term cooling event (∼54 Ma). The highly resolved continental fossil record of the Bighorn Basin, Wyoming, USA, spans this interval and is therefore uniquely suited to examine the long-term effects of temperature change on the two dominant groups in terrestrial ecosystems, plants and insect herbivores. We sampled insect damage on fossil angiosperm leaves at nine well-dated localities that range in age from 52.7 to 59 Ma. A total of 9071 leaves belonging to 107 species were examined for the presence or absence of 71 insect-feeding damage types. Damage richness, frequency, and composition were analyzed on the bulk floras and individual host species. Overall, there was a strong positive correlation between changes in damage richness and changes in estimated temperature, a weak positive relationship for damage frequency and temperature, and no significant correlation for floral diversity. Thus, insect damage richness appears to be more sensitive to past climate change than to plant diversity, although plant diversity in our samples only ranges from 6 to 25 dicot species. The close tracking of the richness of herbivore damage, a presumed proxy for actual insect herbivore richness, to both warming and cooling over a finely divided, extended time interval has profound importance for interpreting the evolution of insects and plant–insect associations in the context of deep time. Our results also indicate that increased insect herbivory is likely to be a net long-term effect of anthropogenic warming.
Article
Plant - arthropod interactions are generally recognized as a major force under the evolution-ary developments in both plants and arthropods, as well as of the terrestrial ecosystems as a whole. Yet surprisingly little was made for exploring the fossil record for documentation and understanding of these fruitful interactions over times. To enlist fossil plants and arthropods coming from one and the same locality or to depict insect traces on fossil leaves is the first step requiring an analytical procedure for further advancements. Since in Israel even the first step had been but timidly made, it was our task, after de-scribing the fossil flora from the richest Cretaceous locality (Krassilov et al., 2005), to provide an inventory of insect body fossils and of the mite and insect traces on fossil plants. Yet we attempted a step further into the realm of structural and functional relationships linking morphology to ecosystem evolution.
Chapter
The Hell Creek and Fort Union Formations in southwestern North Dakota and northwestern South Dakota have yielded a diverse megaflora of 380 species from 158 quarry sites. These sites are situated in a stratigraphic framework, delimited by palynology, magnetostratigraphy, and vertebrate paleontology, that contains both the Cretaceous-Tertiary (K-T) boundary event horizon and stratigraphic evidence for rapid base-level increase. The late Maastrichtian Hell Creek flora is dominated by angiosperms; ferns, fern allies, cycads, ginkgo, and conifers represent <10% of total taxa and specimens. Megafloral extinction at the K-T boundary is extensive, effectively eliminating all dominant plant taxa of the upper Hell Creek Formation. K-T survivorship appears to be greatest in plants that occupied Cretaceous mire facies. The Hell Creek megaflora is heterogeneous with respect to stratigraphic position and sedimentary facies, allowing the recognition of three superposed megafloral zones and two facies-controlled megafloras. Hell Creek vegetation represents an angiospermdominated woodland composed of small-to medium-sized trees, often with lobed leaves. One exception is a diverse angiosperm-dominated herbaceous vegetation associated with large paleochannels in the middle of the formation. The uppermost Hell Creek megaflora zone (HCIII) first occurs near the base of magnetic polarity subchron C29R. The HCIII megaflora is significantly more diverse than earlier Hell Creek floras, and foliar physiognomy suggests a significant climate warming during the final 300-500 k.y. of the Cretaceous. The Paleocene megaflora is depauperate, less heterogeneous than the Cretaceous megaflora, and dominated, in all facies, by taxa that were most common in Cretaceous mire facies.
Article
A high-resolution macrofossil analysis was conducted to reconstruct spruce budworm abundance in an 8600-year-old mire in Saguenay, Québec, Canada. Abundant spruce budworm (Choristoneura fumiferana [Clem.]) faeces recovered in the peat profile suggested endemic and epidemic presence of the insect in the study site since 8240 cal. BP. Important variations in the abundance of faeces were observed, and two exceptional periods of insect activity were delineated, from 6815 to 6480 cal. BP and during the twentieth century. Lepidoptera head capsules were also found in the Lac des Îlets peat profile. They were less abundant and more altered than spruce budworm faeces, but they offered complementary information on insect activity. The long-term perspective achieved with this macrofossil analysis strongly suggests that intense periods of spruce budworm activity were rare events during the Holocene.
Article
In southern Quebec (Charlevoix, Canada), reconstructions of the subalpine insect assemblages were made in environments that were transformed by fire during the late Holocene (since 4500 BP). The ecological requirements of beetle species likely to be found as fossils were studied by collecting living beetles in pitfall traps in forest, suibalpine and alpine environments. The late-Holocene changes of insect assemblages were reconstructed by recovering fossil insects from 13 peat sections. Modem beetle assemblages are valuable indicators of tree cover. Well-developed podzol soils under peat, as well as numerous spruce charcoal remains overlaying the podzol in all sampling sites, suggest that a dense spruce cover was present before the beginning of the accumulation of peat, and was eliminated by fire (4570-800 BP). Ground beetle and bark beetle assemblages at the base of the peat sections contained a mixture of forest and open-environment species, indicating that the postfire environment was a subalpine one with a tree cover of 30-50%. The most recent fire in the area (AD 1915) increased the openness of the landscape (tree cover
Article
1. Some herbivore species periodically undergo damaging, high-density outbreak phases followed by less damaging low-density phases. Others maintain steady, low to moderate density levels that do little damage to their hosts. 2. Two closely related holly leaf-miner species were compared that share many ecological traits and have very similar life cycles, but only one of which exhibits outbreaks. Phytomyza ilicicola in the eastern U.S.A. varied widely in mortality and infestation levels, reaching local densities of over 10 mines per leaf. In contrast, Phytomyza ilicis in the U.K. showed low infestation and high mortality at all sites. Using data from the literature and from field studies, the factors responsible for these contrasting dynamics were sought. 3. Phytomyza ilicicola oviposits into the leaf lamina, and experiences weak larval competition only at high densities. Phytomyza ilicis oviposits into the leaf midrib, which leads to high mortality of young larvae before mine formation. Multiply mined leaves were therefore very common in P. ilicicola but rare in P. ilicis. 4. Differences in the parasitoid complexes of the two systems accounted for further differences in survival to adulthood. The main (larval) parasitoid, which was found to impose high, density-dependent mortality on P. ilicis, is missing on P. ilicicola. It is replaced by an egg–pupal parasitoid, which varies in its impact at differe∼t sites. Multiple emergence of adults from multiply mined leaves is therefore widespread in P. ilicicola but does not occur in P. ilicis. 5. The differences in oviposition behaviour and in the parasitoid complexes are likely to allow P. ilicicola to outbreak when habitat conditions are favourable, while P. ilicis is always tightly regulated.