4/25/17 Ground-dwelling: Where are they found and what are they doing? What do insects do for a living? Insect Ecology Common habits Predators & Ground-nesters • Detritivores and saprophages • Rhizophagous insects • Predators and ground-nesting insects • Decaying wood • Coprophages • Necrophages • Fungivores 1 4/25/17 Decaying Wood Associations with fungi • Most have • Usually associated specialized Sirex wood wasp with fungi – What else is there? structures for • Numerous taxa carrying fungal – Wood wasps, bark spores: beetles, ambrosia mycangia. beetles, scavenger beetles, silken • Why are most fungus beetles, attracted to forest dance flies, termites, fires?: cockroaches. pyrophilous. Coprophages Coprophages • What are these? • These can get to • What are they nuisance levels. feeding on? • Dung dispersers • Why is this such a therefore provide an good lifestyle? important ecosystem • First colonization service. usually dung flies. • Almost always • ~45 independent Scarabaeidae origins of viviparity. Why? 2 4/25/17 Necrophages • Often a very similar lifestyle to coprophages. • Often very closely related. • Most other origins of viviparity here. Necrophages • Often distinct Fungivores succession. • Very useful for forensic • The true entomology. decomposers are • Most initial colonizers are Diptera. fungi. • Later are Coleoptera • There is a whole (e.g. Silphidae). guild of insects • Dried are more that specialize on Coleoptera (e.g. Dermestidae) these. • Final stages are tineid larvae (keratin) 3 4/25/17 Aquatic Insects Hemimetabolous Aquatic Insects • Insecta (even Hexapoda) are plesiomorphically • Some lineages have terrestrial. almost* exclusively • But there have been aquatic naiads. numerous colonizations – Ephemeroptera of the freshwater – Odonata* aquatic environment. – Plecoptera (the only • Far fewer colonizations aquatic of marine aquatic Polyneoptera) environment. • All of these have terrestrial adults. Holometabolous Aquatic Insects Hemimetabolous Aquatic Insects • There are multiple • Colonized aquatic environments much colonizations of more recently. aquatic • Numerous colonizations environments by within numerous orders Heteroptera. • Only two have exclusively* aquatic • Most of these are larvae. also aquatic as • Only some Coleoptera adults. remain aquatic as adults. 4 4/25/17 Holometabolous Aquatic Insects Unusual Aquatic Habitats • Marine environments – Intertidal habitats • Neuroptera: One • Between high and low tide lineage (Sisyridae, • biting flies, plant feeding spongillaflies). insects, detritivores – Littoral habitats – Osmylidae amphibious • Coastal regions with • Coleoptera: Numerous shallow water colonizations • Some midges and beetles throughout. – Open ocean: water striders • Diptera: Numerous feeding on food of terrestrial colonizations, especially origin in Nematocera. • RARE! WHY??? • Lepidoptera: Numerous origins, but NOT common Unusual Habitats Nepenthes • Temporal water bodies (e.g. vernal pools) pitcher – Common in areas with seasonal rainfalls plants • Numerous adaptations – Ability to find ephemeral pools (meteorological cues?) – Desiccation resistant diapause • Very common as eggs • Some with ability to undergo numerous dehydrate/rehydrate cycles: anhydrobiosis • Plant container habitats: Phytotelmata 5 4/25/17 Nepenthes are carnivorous Nepenthes anatomy plants But they rely on DECOMPOSERS How do aquatic insects obtain oxygen? Tracheal System • Atmospheric oxygen – Keep part of body out of water – Carry oxygen into water • Aqueous oxygen – Use of open tracheal system • Adult insects • Immature forms – Use of closed tracheal system • Specialized structures for gas exchange in water • Often adults have open tracheal system 6 4/25/17 Closed Tracheal System Open tracheal system in flies • Respiratory siphons near abdomen or thorax • Different location in mosquito pupa than larva • Gills- lamellar extensions of tracheal system • Found in many insect orders • Gills may be in many places – Base of legs – Abdomen – End of abdomen – How is this analogous to insect ears? Open tracheal system in diving beetles Other air bubble gills • Bubble stored beneath elytra • Water kept away from body through ‘hairs’ or • Gas exchange can occur in water ‘mesh’ • Oxygen diffuses from water to air against body Does the bubble • Usually slow moving insects with low oxygen demand decrease linearly with oxygen consumption? What happens to the exhalation product? 7 4/25/17 Adaptations to nearly anoxic environments Plant Insect Interactions • Hemoglobins – Many larval chironomid midges (Diptera) = bloodworms • Herbivory – Some notonectid bugs (Heteroptera) = backswimmers – Very, very high affinity for oxygen (unlike us) – Only downloads when oxygen concentrations in tissues decrease, not when tissues become acidic • Plant reproduction • Domatia Evolution of Insect Herbivory Cretaceous • Early hexapods contact • What major plant plant parts in soil radiation occurred in • Vascular plants the Cretaceous,145 diversfied 300 MYA – 65 mya? • Fossil traces of insect eating appear shortly • Radiations thereafter • Early herbivores often beetles 8 4/25/17 Challenges of phytophagy Diet Breadth • Clinging to • Monophagous vegetation – Feeds on one plant • Subject to taxon desiccation • Oligophagous • Inferior diet – Feeds on only a few plant taxa • Plant defenses • Polyphagous – Feeds on many plant taxa How Insects Feed on Plants Chewing & Leaf rolling • Chewing • 20-45% of foliage may be normally lost in some • Sap sucking plant taxa • Flower feeding • Up to 100% in outbreak • Root or shoot conditions feeding Mining • What risks does leaf chewing have? • Boring • How might leaf rolling • Gall induction combat these? • Seed predation 9 4/25/17 Mining Boring Living leaves, consumes parenchyma Deep tissue Living or decaying/dead tissue What do they consume? Sap-sucking Gall induction • Almost exclusively • Kinds of galls Hemiptera. – Covering galls • What structures do – Filz galls they feed from? – Pouch galls • Very low quality food – Mark galls source (especially – Pit galls xylem). – Bud and rosette galls • How do they deal with this? 10 4/25/17 Process Seed predation • initiation • Most extreme phytophagy • growth – Kills entire plant • insects alter plant – Converts material intended for plant growth patterns in offspring into insect some way offspring • Seed harvesting and external consumption – How could this be a mutualism? • Development inside the seeds Plant defenses Physical defenses • Physical • What are some that you can think of? • Chemical • Mutualisms • Life history • Physical defenses against insects more traits subtle – Glandular trichones – Stellate hairs – Thick wax – Silica crystals – Sclereids 11 4/25/17 Chemical defenses Plant apparency • Plants are apparent The image cannot be displayed. Why is if they are easy to Your • Secondary plant computer mustard find (do not require may not have compounds enough pungent? unique neural memory to – Defensive chemicals open the image, or the – Not principally metabolic searching image may have been (although might be mechanisms by corrupted. derived from these) L-canavanine enemies). • Effects: Inhibits growth in – Repellant or inhibit most insects oviposition or feeding – Toxic Plant apparency Plant apparency • Plants are • Quantitative defenses: unapparent if they – Quantitative defenses: dose-dependent, defend are difficult to find against generalist (require unique enemies neural searching – Which types of plants will have these? mechanisms by enemies). 12 4/25/17 Plant apparency Mutualisms • Qualitative • Almost all plant defenses: defense mutualisms – Qualitative defenses: involve ants lethal in small doses, – E.g. Cecropia and defend against Acacia specialized enemies. • Generally provide – What kinds of plants will have these? Why? some domatia for the colony • What is the mutualism? Life history: Masting Predator satiation and Masting • Predator saturation • Seed production by Seed production • Reproduction by plant % seeds consumed populations occurs plant is numerical (or simultaneously and in linear). massive numbers • Predator satiation is • Produce more seeds the result a than intrinsic functional response. reproductive capacity of • Results in insects can keep up Insect response with decreasing % of # seeds consumed prey population • Some seeds will escape insect predation being consumed at high density. Seed density 13 4/25/17 Insect-Plant Interactions Coevolution • Evolution • Evolutionary change (genetic change) in one – 50% of all insects species causes evolutionary change in feed on plants another – This great – Hot topic in evolutionary biology diversification of – Predators vs prey- insect-insect interactions insects occurred – Hosts vs parasites mostly only within – Parasitoids and host insects last 60 million yrs. – Bacteria versus host insect – Why? – Mimicry- Batesian and Mullerian – Mutualisms- plants and pollinators Coevolution Coevolution • Pairwise coevolution • Diffuse coevolution – Evolution of traits in one species cause – Reciprocal evolutionary change among changes in another groups of species rather than specific pairs – These changes in the other species cause – Specificity of response not as important changes in the first – Reciprocal interactions proposed – May cause speciation 14 4/25/17 Cost of Secondary Role of Plant Chemicals Metabolite Production • Example of nicotine biosynthesis • Plants possess many compounds not – Requires several needed for primary metabolism biosynthetic steps – Requires nitrogen (secondary