module 3 insect biodiveristy

discontinuous growth

due to exoskelton, fact that exoskelton cuticle, new one secreted hardens and determines size, every molt body size increases, body cant gradually grow

molting

shedding of exoskeleton for growth, two stages
apolysis (1st) - separation of epidermis from cuticle; first

ecdysis (2nd) casting of old cuticle second

instars (3rd)

period between molts, insect is feeding and go about business not molting this is instar, fixed number in holometabolist

imago (8th)

adult instar

subimago (4th)

juvinelle instars

pupation (5th)

last juvenile instar in holometabolous organisms

eclosion (6th)

release from cuticle of pupae

ternal stage (7th)

adult stage before sclerotization, a brief but important stage because insect vulnerable

hormone

Chemical messengers, made in organism that transport to influnce physiological processes

neurosecretory cells

modified neurons make hormones

corpous cardiacum

behind brain, hormone store here

prothoracic gland

x like and makes ecodysin and induces molting

corpus allatum

either side of foregut; stores juvenile hormones

ecdysone

A hormone that helps control metamorphosis in insects triggers ecdysis: the process of molting in the prothoracic gland

juvinelle hormone

keeps insect as larvae or if none lets it become an adult this is in corpus allatum

larvae to larvae molt

this is where insect just grows but wont become puppa or adult

larvae to pupal molt

pupation

larval to larval molt

high Juvinelle hormones and ecdoysin

larval to pupa

ecodysin and low JH

pupa to adult

no JH and ecodysin

ecdyosin always triggers a molt

different types of development

ametabolous

hemimetabolous

holometabolous

ametaboly- not fixed number of molts, no change among instars except adult genetialia is dif and continue to molt as imagos (not true for most insects such as hemi or holo metabolists) in ametabolist, egg-nymph- adult

hemimetabolist- determinant growth, fixed number of molts in species , egg stage fixed number of nymph stages and adult stage the instars nymph look like adult

holometabolist- fixed number of instars drmaatic changes between larva pupa and adult this is complete metamorphsis, egg then instars and instars are called larvae ( only juvinille instars are larvae in holometabolist)

adult=imago

wing formation

important in insects this involves imaginal disk in juvinille instars in larvae devolop into wing and disk is preformation of wing that occur within larval stage, as insect reaches pupation the prep in larval stage the cells invaginate and grow and divide inward to make structure like wing, during metamorphsis is formation of wing happens prior to puptaion

all holometabolist go through eggs larva pupa and adult

legs

apods- no leg

oligipod- true legs have thoracic legs

polypod- have legs on thorax but also have prolegs on abdominal

can see with puppa where certain structures are

headcapsule

locked in inderminate growth until molt, catipllar head big compared to body but as body grows the head stays same by time ready for molt head will look tiny, can look at larvae head and determine where its at for molt

apolysis

Separation of old cuticle from epidermis

Ecdysis

secretes new cuticle

Development rate

how quickly an insect passes through diffrent life stages, rate can be determined by genetics (dif species dif rates) variation within spceies due to envio factors food quantity quality but mostly temprature

ectothermic

internal temp determined by external heat sources environment
poikilothermic (a type of ectotherm) - internal temp very variable
affects development rate

development rate

-food quantity/quality, moisture, TEMPERATURE!!!
respect to physiological time this is amount of heat over time to complete stages of development, measured in degree days over devolopmental treshold, ex treshold is 10 C, if its above it it continues to devolop otherwise no longer progressing, how many degrees is how many days over

generation time

voltanism- generations per year

semivoltine- takes more than 1 year for generation

uni- 1 per year

bi-2 per year

multi-many per year

Voltanism

univoltinehappens in temprate climates, fall winter spring too cold does all devolopment in summer,

multivolt- unifrom resources, insect small and fast devoloping

voltanism can be fixed or enviormentally devoloped

parthenogenesis

Reproduction without sex, give

birth to live young are: vivaparous

telescoping generations- meaning because no sex for reproduction, egg within it already developing, generation times very quick bc no mating, aphids can have gen time of 4-5 days

periodic cicades

semivolting the whole lifecycle can be many many years and results in long gen times often it is a prime number 13 year 17 years go through large period where they dont devolop, way of them escaping preadtors if bunch appear after 13 years many many outnumber predators, if predators on any cycle other it will not line up w cicada and will starve the predator may concide one time but wont the other time

breaks in development

quiescene - halted or slowed development (optional) based on environmental conditions (facultative)

facultative - optional, a choice made for different developmental pathways or life stages based on environment or other factors

diapause- arrested development and adaptive physiological changes. Development returns with appropriate stimuli, which can be years or days (obligatory, required, faculative)

most insects in temperate climates in winter where it snows it will completly shut down, diapause-normally in egg or pupil stage

Polymorphism

diffrent discrete forms or morphs of insect

genetic polymorphism- form not determined by enviornment like sex male vs female

enviornmental polymorphism is aka polyphenism this is determined by enviornemnt also called phenotphic plasticity (phenotype can change)

ex is ants same species same colony individual of species with one genotype can become any cast based on enviornment

systematics

the study of diversity of organisms with the purpose of deriving their relationships, and evolutionary history

Taxonomy

description classification- (looking at insect and try to figure out what is it and then classifying it)

identification collection

phylogeny

relationships among taxa

description and classification

Recognizing an insect is new

describing it what charcteristics does it have, easily obvious or disect it look at gentialic morphology

naming it

deciding what taxonomic group it belongs to classify what genus what species

Holotype

a single type specimen upon which the description and name of a new species is based. is this species dif or same need actual specimen for benchmark of species

Paratype

a specimen not formally designated as a type but cited along with the type collection in the original description of a species, look at all these are other examples etc

identification

through id services experts look at group and tell u with confidence what it is, do id use identifcation keys but also devolop keys to help non experts

also use dna barcoding- single fragment dna taken coi gene this is benchmark for dna barcoding look at sequnce of this in all animals and library of sequnces has been accumlated and look at sequnce and determine what we have, but dna sometimes not clear at the relationship between genetic varation, sequnce data can help expert determine order etc

collection

collect insects from enviornment or go to dif enviornemnts and sample biodiversity, look at forst vs shrubland look at whats on plant underneath etc, collect material and then curate and identify and label, update nomenclature, important part is specimen loans, refrence material in dif collection can loan it to them

Phylogeny

infering relationships

first lec there is lineaun classification based upon similarity

-kingdom

phylum

class

order

family

genus

species

then darwin took this and added evolutionary context making kingdoms old and species young, all species in genus share evolutinary history and that happens back and all genera in same family they evolved from same ancestor and so on and so on

Phylogeny

an evolutionary tree a hypothesis off relationships among taxa, taxonomic group= any group deemed diffrent from other groups

these trees are hypothesis

there are tips these are species we see today, then there are terminal branches this leads to the tip and then internal branch lead to multiple tips

internal nodes- all internal this is where tree branches

base of tree is the root

can be dif types of groups

when looking at tree the nodes can be flipped

order of taxa not important as AB CD EF can be BA DC FE does not change branching pattern

Apamorphy

trait unique to a taxa like halteres on flies (trait only in flies and nobody else)

imagine then that halteres evolve along end branch then

Synapomorphy

a trait shared with multiple taxa its unqie to group of taxa shared with common ancestor

ancestral state

the infered traits of an ancestral taxa

monophyletic group

a group of taxa that are all descendants of a common ancestor and includes all descendants of that ancestor

Homoplasy

a charcter shared by a set of species but not by their common ancestor but rather due to evoluntariry convergence

paraphyletic group

a group that includes some but not all descendants of a common ancestor and thus not monophyletic

phylogenetics data

-morphology including anatomy, physiology, and biochemistry

DNA sequences more closely related with relativity

biogeography- where a species can occur

approach

use maximum parsimony- simple possible explination

Calibrated phylogeny

assigning ages to internal nodes based on molecular clocks, = rates of dna sequnce change fossils and biogeography assign when did the holometabolism evolve

Evolution

insect evolution trace evolutionary history at base of all life to arthropods and hexapods

key innovation

an evolutionary change playing an important role of success in linaege infered from co occurence of evolved traits with rapid diversification where group of organisms evolves a trait and lots of diversification and many new species

4 we talk about is tracheal system

flight

piercing sucking mouth

metamorphsis

Homology

homology is shared between traits in diffrent species due to shared ancestory , relates to symnapmorphy

Analogy

similar look due to similar function due to evolutionary convergence

tracheal system

ancestral condition of hexapods is shred with crusctean, tracheal system evolves within hexapods

anestor-no trachea gas exchange across cuticular surface, hemocyanin respiratory pigment in hemolphymph and it circulates through sinuses, still have last part but hexapods now have trachea and spiracles

aquatic based hypothesis

tracheal system evolved within water or on land, aquatic on water, air filled trachea, spaces formed between cuticle to prevent ion exchange between hemolpyhm and enviornment these are voids to seperate out from in and voids evolved to prevent seperation and then co opted and became gas exchange

terrestrial based hypothesis

invagination of cuticilar surface and internal elaborations post invasion of terrestrial habitats

evidence- all extant species of insects and noninsects all terestial

no fossil evidence of aquatic form

parallel dynamics that follow this in other arthopod linages

evolution of trachea- key innovation because allows movement to land, all hexapods are terestial except some return to water this is analogus

flight

ancestral: flightless; not from the loss of limbs

1.) paranota- thoracic segments that evolved from nota

2.) epicoxa - preexisting mobile structures on the thorax —> wings

3.) serial homology - w/ abdominal gills, dif species evolve from common ancestor, gene expression from a different part of the body is expressed —> gills in thorax —> wings

evolution of indirect flight

ancestral-paleoptera (direct flight)

direct- muscles directly move the wings
odonata - direct flight

most insects use indirect flight
indirect flight - muscles compress and extend thorax, indirectly moving wings

key innovation because finer control of wings and more efficient allow for lift with less muscle mass allows smaller insects to fly

evolution of indirect flight that leads to diversity of insects

piercing-sucking mouthparts

piercing sucking mouth part- belong to paraneoptra and polyneoptra

3 major clades within neoptra

paraneoptra- piercing sucking mouth part evolved here before ancestral condition was chewing mouthpart, these are homologus

derived mouthparts- slender elongated maxillary lacina(mouth part now straw), enlarged cibarium (works to sucking pump) create suction that draws fluid

psocoptera- rudimentary transitional in these diffrences

thiraptera- cell content they puncture the cell of plant and feed

hemiptera- well devoloped piercing sucking, needle like they insert into pray and they lubricate and secrete saliva to help position within host organism feed on liquid from host

allows insects to feed on novel resources

Evolution of complete metamorphosis

the ancestral state was incomplete metamorphesis. This separates holometabolists

2 hypotheses

1) (INCORRECT) pupa evolved de novo (new life stage) larvae are homologus to nymph, each larval instar in holometabolist is the same as nymphal instars of hemimetabolists. The pupa is brand new thing

2) (CURRENT) Larvae evolve from a pronymph, larvae before nymph stage, pupa is homologous to all nymph stages combined

hemi - egg - nymph- adult

holo - egg-larvae-puppa-adult

insects

** WATCH VIDEOS !!!

Pre-adaptation of flight

Protowings- hypothesized ancestral structures or precursors to the modern wings of insects

original non flight origin: protection of legs, covers for spiracles, thermoregulation, sexual display, predator avoidance

selective pressures —> flight

Holometabolism

holometabolist metamorphosis

this is a key innovation because it allows for larvae to have a separate lifestyle separate to the adult. (two body plans, which separates the needs of the insect)

adult can focus on reproduction and dispersal

Protowings

possible: covering for legs/spiracles, flap/thermoregulation, surface area releases more heat, sexual display, predator avoidance

aerodynamics!! (occurs after enlargement)

larger because . . .

1. floating - fall from plant, more surface area

2.paragliding, stability in falling

3. running jumping to flying- leap and air projection

4. surface sailing - help moving across the water

key innovation: movement into new habitats and use of new resources