Binciken yiwuwar jama'a

ƙididdigar ƙididdiga (**PVA**) hanya ce ta ƙididdigan ƙididdigatattun ƙididdiga da ake amfani da ita akai-akai a cikin ilmin halitta. An bayyana shi a al'ada a matsayin tsari wanda ke ƙayyade yiwuwar cewa yawan jama'a zai ƙare a cikin shekaru da aka ba da yawa. Kwanan nan, an bayyana PVA a matsayin auren ilimin muhalli da kididdiga wanda ke tattare da halaye na jinsuna da bambancin muhalli don yin hasashen lafiyar jama'a da haɗarin halaka. Kowane PVA an haɓaka shi ne don yawan jama'a ko jinsuna, kuma saboda haka, kowane PVA na musamman ne. Babban burin da ake ciki yayin gudanar da PVA shine tabbatar da cewa yawan jinsin yana ci gaba da rayuwa na dogon lokaci.

## Amfani da shi
Ana amfani da nazarin yiwuwar yawan jama'a (PVA) don kimanta yiwuwar lalacewar yawan jamaʼa kuma ya nuna gaggawa na kokarin farfadowa, da kuma gano mahimman matakai na rayuwa ko matakai waɗanda ya kamata su zama mayar da hankali ga kokarin farfaro. Hakanan ana amfani da PVA don gano abubuwan da ke haifar da yawan jama'a, kwatanta zaɓuɓɓukan gudanarwa da aka tsara da kuma tantance ƙoƙarin dawo da yanzu. Ana amfani da PVA akai-akai a cikin kula da nau'in da ke cikin haɗari don haɓaka shirin aiki, tsara fa'idodi da abubuwan da suka dace na yanayin gudanarwa daban-daban, da kuma tantance tasirin tasirin asarar mazaunin.

## Tarihi
A cikin shekarun 1970s, Yellowstone National Park ya kasance cibiyar muhawara mai zafi game da shawarwari daban-daban don sarrafa matsalar wurin shakatawa (*Ursus arctos*). A shekara ta 1978, Mark Shaffer ya ba da shawarar samfurin ga grizzlies wanda ya haɗa da bambancin bazuwar, da lissafin yiwuwar lalacewa da mafi ƙarancin girman yawan jama'a. PVA na farko an ba da shi ga Shaffer . 

PVA ta sami shahara a Amurka yayin da hukumomin tarayya da masu ilimin muhalli suka buƙaci hanyoyin don kimanta haɗarin halaka da yiwuwar sakamakon yanke shawara na gudanarwa, musamman daidai da Dokar Halitta ta 1973, da Dokar Gudanar da dazuzzuka ta Kasa ta 1976.

A cikin 1986, Gilpin da Soulé sun fadada ma'anar PVA don haɗawa da dakarun hulɗa waɗanda ke shafar yiwuwar yawan jama'a, gami da kwayoyin halitta. Amfani da PVA ya karu sosai a ƙarshen 1980s da farkon 1990s biyo bayan ci gaba a cikin kwamfutocin mutum da kunshin software.

## Misalan
Fender's blue butterfly (*Icaricia icarioides*) da ke cikin haɗari an tantance shi kwanan nan tare da burin samar da ƙarin bayani ga Hukumar Kifi da namun daji ta Amurka, wanda ke haɓaka shirin farfadowa ga nau'in. PVA ta kammala cewa jinsin ya fi fuskantar haɗarin halaka fiye da yadda aka yi tunani a baya kuma ya gano manyan wuraren da ya kamata a mayar da hankali ga kokarin farfadowa. PVA ta kuma nuna cewa saboda yawan malam buɗe ido yana canzawa ko'ina daga shekara zuwa shekara, don hana yawan jama'a daga ɓacewa dole ne a kiyaye mafi ƙarancin ƙimar ƙaruwa ta shekara-shekara fiye da matakan da aka ɗauka a matsayin karɓa ga wasu nau'o'in.

Bayan barkewar kwayar cutar canine distemper na baya-bayan nan, an yi PVA ga fox tsibiri mai hatsarin gaske (Urocyon littoralis) na tsibirin Santa Catalina, California.  Yawan jama'ar fox na tsibirin Santa Catalina na musamman ya ƙunshi ƙabilu biyu waɗanda ɗan isthmus ya raba su, tare da yawan jama'ar gabas da ke cikin haɗarin halaka fiye da yawan jama'ar yamma.  An gudanar da PVA tare da maƙasudin 1) kimanta haɗarin lalata fox na tsibirin, 2) ƙididdige halayen fox na tsibirin ga abubuwan da suka faru na bala'i, da 3) kimanta ƙoƙarin dawo da kwanan nan wanda ya haɗa da sakin foxes na fursunoni da jigilar yara na daji daga yamma zuwa gabas.  Sakamakon PVA ya ƙaddamar da cewa fox na tsibirin har yanzu yana cikin haɗari mai mahimmanci na lalacewa, kuma yana da matukar damuwa ga bala'i da ke faruwa fiye da sau ɗaya a kowace shekara 20.  Bugu da ƙari kuma, haɗarin ɓarna da girman yawan jama'a na gaba a ɓangarorin biyu na tsibirin sun dogara sosai kan adadin foxes da aka saki da jigilar su kowace shekara.

Hakanan za'a iya amfani da PVAs a haɗe tare da nazarin hankali don gano waɗanne mahimmin ƙimar da ke da alaƙa mafi girman tasiri akan haɓakar yawan jama'a da sauran matakan yuwuwar yawan jama'a.  Misali, binciken da Manlik et al.  (2016) yayi hasashen yuwuwar yawan dolphin bola biyu a Yammacin Ostiraliya kuma an gano haifuwa a matsayin mafi girman tasiri akan hasashen waɗannan al'ummomin.  Daya daga cikin al'ummomin biyu an yi hasashen cewa za ta tsaya tsayin daka, yayin da sauran jama'ar da aka yi hasashen za ta ragu, idan ta kebanta da sauran al'ummomin kuma karancin haihuwa ya ci gaba.  Bambancin yuwuwa tsakanin karatun biyu ya kasance da farko saboda bambance-bambance a cikin haifuwa ba rayuwa ba.  Har ila yau, binciken ya nuna cewa bambancin ɗan lokaci a cikin haifuwa yana da tasiri mai yawa akan haɓakar yawan jama'a fiye da bambancin ɗan lokaci a cikin rayuwa..

## Rikici
Akwai muhawara kuma ba a warware su ba game da amfani da PVA a cikin ilmin halitta na kiyayewa da kuma ikon PVA na tantance haɗarin halaka daidai.

Babban adadin bayanan filin yana da kyawawa don PVA;  wasu masu ra'ayin mazan jiya sun yi kiyasin cewa don ƙayyadadden ƙimayar yuwuwar bacewa wanda zai tsawaita shekaru T zuwa gaba, ana buƙatar shekaru biyar zuwa goma na bayanai.  Rubutun bayanai na irin wannan girman yawanci ba sa samuwa ga nau'ikan da ba kasafai ba;  an kiyasta cewa bayanan da suka dace don PVA yana samuwa don kawai 2% na nau'in tsuntsaye masu barazana.  PVA don nau'ikan da ke cikin haɗari da haɗari musamman matsala ce kamar yadda ikon tsinkaya na PVA ya faɗi da ƙarfi tare da ƙarancin bayanan bayanai.  Ellner et al.  (2002) yayi jayayya cewa PVA yana da ƙananan ƙima a cikin irin waɗannan yanayi kuma an maye gurbinsa da wasu hanyoyi.  Wasu suna jayayya cewa PVA ya kasance mafi kyawun kayan aiki don kimanta haɗarin ɓarna, musamman tare da yin amfani da ƙirar ƙirar hankali.

Ko da tare da isasshen bayanan, yana yiwuwa cewa PVA har yanzu yana da manyan kurakurai a cikin tsinkayen ƙarancin ƙarewa. Ba zai yiwu a haɗa duk yiwuwar nan gaba a cikin PVA ba: wuraren zama na iya canzawa, bala'o'i na iya faruwa, ana iya gabatar da sabbin cututtuka. Za'a iya inganta amfani da PVA ta hanyar samfuran samfuran da yawa tare da saiti daban-daban na zato ciki har da hasashen nan gaba. Wasu sun fi son amfani da PVA koyaushe a cikin nazarin dangi na fa'idodin wasu tsare-tsaren gudanarwa, kamar kwatanta tsare-tsare na gudanar da albarkatun da aka tsara.

An gwada daidaito na PVAs a cikin 'yan binciken da aka yi a baya. Misali, wani binciken da ya kwatanta tsinkayen samfurin PVA tare da ainihin makomar 21 da aka yi nazari sosai, ya nuna cewa tsinkayen ci gaba daidai ne, idan masu canji na shigarwa sun dogara ne akan bayanan sauti, amma sun nuna muhimmancin fahimtar dogaro da yawa (Brook et al. 2000).  Har ila yau, McCarthey et al. (2003)  sun nuna cewa tsinkayen PVA suna da daidaito, lokacin da suka dogara da bayanan dogon lokaci. Duk da haka, amfanin PVA ya fi dacewa da iyawarsa na ganowa da kimanta yiwuwar barazanar, fiye da yin tsinkaya na dogon lokaci, tsinkaya (Akçakaya & Sjögren-Gulve 2000). 

## Hanyoyin da za su bi nan gaba
Improvements to PVA likely to occur in the near future include: 1) creating a fixed definition of PVA and scientific standards of quality by which all PVA are judged and 2) incorporating recent genetic advances into PVA.&#x5B;**&#x5D;